I often get accused of being an enemy to philosophy, but that is not correct. I'm a pretty serious fan of that discipline and respectful of its contributions to human knowledge. I have become, however, an outright enemy of the philosophy of religion (though not philosophers of religion), a field that I now refer to as "god-bothering" (because these are people who bother with God).
I make no secret of these facts, of course, and as it worked out, this led to me being asked earlier on The Twitters why there are atheist philosophers of religion. Though I can't be sure of the tone, I get the impression (and am taking it for the purposes here) that the question was meant to be a challenge to my statement that philosophers of religion are god-bothering, which is something we should no longer do. (Full disclosure: I also said that philosophers of religion should have credentialing letters D.M. after their names, for "Dungeon Master.")
At any rate, whatever the tone of the question, I think it's one worth a little commentary, though I'm certainly left to speculate on the matter (partly from my own experience in getting interested in the philosophy of religion and partly by inferring from similar situations). We'll call these educated guesses, then.
I have a feeling that many people, upon going post-faith, need to decompress, if I might use that term. They've got a lot of stuff pent up in them, often from discovering that they've been duped into living a lie and from living in a religiously dominated culture and society (at least in much of the United States). By the time someone goes full-atheist, there's a whole lot of stuff that just needs to come out, and so it does. Sometimes this might have something to do with really, really, really making sure hell is a lie--that fear can be instilled pretty deeply--and sometimes it may not. At any rate, there's a lot of what I call throwing rocks at the cathedral that goes on when people first step outside of it.
One way that particular kinds of people deal with this cognitive shift, which probably involves a lot of dissonance reduction, is by looking into every reason they can find to support the way they think, especially if one is getting challenged for throwing rocks at the cathedral. Not everyone does this, of course, but lots do. Others have heard the theological and apologetic twaddle for much or all of their lives, some even studying it, and have even more decompressing to do. At any rate, this will drive many philosophically inclined people to become very interested in the philosophy of religion from the atheistic side. Some clever individuals get involved in it and will probably keep it up at least until their decompressing is over, which, as I've suggested, probably runs the deeper for having been more invested in the philosophical arguments that pretend to favor religious views (none do--they all are games of "hide the turd").
This is one reason that there would be atheists that god-bother--deconverted apologists, theologians, and the likes, who try to turn the tables by engaging their former peers on their own terms. Some of these would be professionals, and some would be amateurs. At any rate, this is one reason that we should expect to see atheist god-botherers.
Whether triggered by decompression or by the fact that until relatively recently it was probably a legitimately important endeavor--I usually say around 2010 or 2011 as Dawkins's The God Delusion kind of stopped being controversial and became part of the cultural furniture, this also being (probably coincidentally) when former philosopher of religion Keith Parsons gave up the field--simple momentum would explain why there are atheist philosophers of religion.
By momentum, I mean that there are professional and amateur philosophers of religion that date back into the time when the death of the field hadn't really occurred yet, and these people became very involved (often professionally) in the effort. You really can't expect many people whose paychecks or professional reputations are wrapped up in a field to all suddenly agree that it died and then jump ship. Some of these people still work in the field in which they earn a living and/or made a name (sometimes called atheologians, which is a term that should be disparaged). Keith Parsons, as mentioned, is one example of someone who left the effort to pursue other philosophical avenues, but particularly with a change that is so new, we should expect to see lots of them out there still.
Consider for a moment what it would be like to be someone who,
professional or amateur, worked very hard in the god-bothering field,
built something of a name for him- or herself, and now faces the fact
that the field is dying. That investment is real, and it's hard to break
away from, perhaps requiring reinventing oneself rather radically while
abandoning something that the individual is both good at and recognized
for. This is momentum, and it explains some atheist god-botherers, no
Additionally, the theologians who try to pass themselves off as philosophers of religion certainly don't stop publishing this stuff, and so it feels like it needs some kind of a rebuttal. Indeed, so long as the journals themselves are respected in the broader philosophical and academic communities, those rebuttals are rather necessary. The momentum there also contributes to engagement in painfully necessary god-bothering on the part of atheists and, unfortunately, probably must until the academy and the philosophy world declare the field properly dead and render its journals properly embarrassing to continue publishing in (this, I understand, isn't terribly far from the case, but it isn't fully the case yet).
Of course, even on the atheist side, the field still has some modicum of academic respectability to it--which is quickly dwindling despite the efforts of amateur enthusiasts. In fact, it seems to be benefiting from the atheism boom following the success of the "unsophisticated" New Atheists at reaching people on this point in the right way at a critical time. Since there are lots of atheists decompressing or otherwise interested in seeing theistic arguments debunked, many of whom are smart and philosophically inclined, it only makes sense that many of them would take up god-bothering so long as it seems to be a field of genuine academic importance.
Because of the circumstances of our times--an uprising of atheism and a concomitant surge of apologetic fervor to defend dying beliefs--arguments for God have found what seems to be renewed interest (interest that some theologians might have helped to manufacture, though this is hard to say). That these arguments are wrong seems to be almost a given, at least among atheists, but saying how they're wrong is sometimes quite difficult. (Compare Zeno's Dichotomy Paradox, which calculus does not actually solve--it's easy to see that it must be wrong because we can move, but that doesn't show us how it is wrong, a point upon which debate continues to this day.) Cracking the nut on religious arguments presents an interesting and engaging puzzle, and puzzles, by their very nature, are often alluring. Some people want to try to solve these puzzles (I am that kind of person and did this for some time, so I know these people exist), and so the draw of the puzzle would be another reason that there are atheists that god-bother (as I did for a while).
As indicated, I completely understand this drive, and I have no qualms with anyone engaging in whatever kind of intellectual entertainment they like. That doesn't justify treating it as a serious academic endeavor, however, even if it does raise its respectability enough to keep it going as one. Also, it doesn't imply that anyone needs to take this form of entertainment upon themselves or even to take it seriously. (This is a serious problem as many god-bothering enthusiasts on the Internet browbeat people for not falling under the spell of "we must engage the best arguments for theism," as if there actually are any good ones.) I like puzzles. That's why I got a PhD in math, but I don't get so wrapped up in them that I think they're important for anyone else.
So, being interested in certain kinds of puzzles--finding the ever-present turd in theistic arguments, as it were--helps explain why there are atheist god-botherers.
Thinking it helps
It's super-easy to get it into your head that the "we have to engage their best arguments if we want to break the spell of belief" line is true. It's almost certainly not. Take conservative Christian theologian and apologist William Lane Craig for example: he bases his belief ultimately on the "self-authenticating witness of the Holy Spirit," which he considers an "intrinsic defeater-defeater." That means he thinks this internal feeling of the Holy Ghost defeats all defeaters. Good luck denting his belief by beating his arguments. He flatly says it's not possible. He even explained (unsurprisingly) how this works: anything that could convince him that he's wrong is contingent upon the particulars of our circumstances and therefore unlikely to be universally true. Atheist god-botherers seem to be missing the point that belief typically doesn't follow the arguments; the arguments are rationalizations of the beliefs. That there are people (who self-style as being imminently rational, no less) who miss this point is a reason that there are atheist god-botherers.
Seriously, Craig's case is as clear an explication that beating their arguments doesn't beat theism as there can be. The thought is that the pastors follow the theologians and apologists, and the flocks follow the pastors, so if you just beat the theologians at their best, the rest falls like dominoes. Craig, and Plantinga like him, with his nonsense sensus divinatatis, shows us why this is spurious thinking. Even the case of Tim McGrew shows what a farce it is. McGrew is an epistemologist! That means McGrew's job as a philosopher is to make sense of how we know what we can know and what we can't know, and he adamantly believes in Christianity! A clever little Bayesian argument about the unlikeliness that God exists, though, is sure to topple these guys... (and I have a lovely ocean-facing villa in Arizona for sale).
Either way, mistakenly believing that all people are all of philosophically minded enough, rational enough, intellectually honest enough, and reliant enough upon the content of these arguments for the contents of their beliefs to be able to be defeated by cleverer arguments probably keeps some atheist god-botherers going. This also includes a belief that these kinds of arguments would influence everyday believers (hint: they won't; the vast majority of everyday believers don't know philosophy, don't care about philosophy, don't trust philosophical mumbo-jumbo, don't believe for rational reasons, haven't heard the apologetics, and would immediately turn on faith-stealing evil philosophers just the way Paul says to in the Bible they think is ineffably true).
Many people who were previously religious or who live in predominantly religious cultures run into all kinds of religious crap all the time, and so even after an initial phase of decompressing, more rocks sometimes need to get lobbed at the cathedral. Doing so sometimes takes the form of cleverness that probably falls, broadly, under the philosophy of religion umbrella. I'd guess this encourages atheist god-botherers to jockey for status, notice, or a feeling of self-worth by doing something similar and doing it well.
The thing is, throwing rocks at the cathedral, even philosophically, isn't really god-bothering. It isn't meant to be taken really seriously--it's just thrown out to wheedle doubt, feel clever, get a laugh, or some such simple motivation. God-bothering is about bothering to construct serious arguments that are intended to be taken seriously. Throwing a philosophical rock at the cathedral doesn't really qualify.
I hate to mention this one, but I think that it's actually possible that there are atheist god-botherers purely out of spite--for atheists. There seem to be two identifiable groups that (amateur) atheist god-botherers seem to be pretty mad at, and it's probable that at least some professionals are mad at one of these groups. The first group is the wide swath of everyday folks on the Internet who like to get into arguments about religion but do not care about using anything like philosophical savvy, careful terminology, or, often enough, anything like arguments that make sense. This seems to infuriate god-botherers, so far as I can tell, and doubling down on their god-bothering (and browbeating about it) seems to be a result.
The other group, the one that amateur and professional atheist god-botherers may unite in addressing with scorn are the so-called New Atheists, particularly the famous ones. Richard Dawkins and Sam Harris, in particular, are attacked relentlessly for an accused lack of philosophical savvy, and many atheist god-botherers seem to have made it an outright quest of theirs to disparage them for it. Some even explicitly work to do so in at least equal measure to what they give theologians. I strongly suspect--despite their protestations that are sure to follow--that spite is a recognizable element in this behavior.
Dawkins and Harris, along with Hitchens (Dennett being left out here because he is a philosopher, though not much of a god-botherer), conclusively proved that god-bothering isn't nearly as effective a method of helping break the spell (that's for Dennett) of faith as is the New Atheist approach, however that might be characterized (as "bad for atheism" by some atheist god-botherers). Dawkins's The God Delusion, which is "middlebrow" and not meant to be philosophically sophisticated, is the nearest of their books to doing any god-bothering, and as god-botherers are extraordinarily wont to point out, they can do that job far better than Dawkins did.
It must drive some of them absolutely batty that Dawkins sold millions of copies and positively impacted millions of lives while comparatively very few give two winks about all the careful god-bothering out there, which presumably takes so much more effort. I hate to say so, but because it offers these batty-driven people a reason to crap on Dawkins, et al., they remain atheist god-botherers, sharpening their little god-bothering spears in part so that they can show the world how much more sophisticated and ecumenical than the great Richard Dawkins they are.
There are probably other reasons that there are atheist god-botherers out there, professional and amateur, ones that I haven't taken time to account for here. That's beside the point (though adding them in the comments is strongly welcomed). The point is that there are reasons that aren't the "legitimacy" of the field that there are atheist god-botherers, so the existence of atheist god-bothering doesn't imply that the field is legitimate.
To the best I can tell, in fact, there are only reasons other than the "legitimacy" of the field that there would be any atheist god-botherers; the field simply isn't legitimate and probably does more to help theologians and apologists in their efforts than to defeat them. Of course, to be fair, it's still pretty soon after the death of god-bothering, so maybe some of them just haven't read the obituary yet. On that note, I suppose, do share.