Some kind of minimal deism (motivated by the cosmological argument) seems reasonable enough. But (as I've previously noted) it's a pretty big leap from there to theism, and an even bigger leap to the particular historical and theological claims of religions like Christianity.
Kevin's defense of theism's credibility is rather quick:
It is simply obvious that theism is reasonable to anyone who is acquainted with contemporary philosophy of religion. Nearly all atheists in the literature acknowledge that theistic belief is at least sometimes epistemically justified.
A major worry about appealing to the consensus of philosophers of religion is that this can plausibly be entirely explained by selection effects: it would be odd to specialize in philosophy of religion if one considered it a settled issue. And if (nearly) the only people who bother to enter the field are those who are antecedently inclined to take religion seriously, their consensus on this point can hardly be taken as evidence that the rest of us ought to do likewise. So, the crucial question is instead whether further exposure to the philosophy of religion would cause other atheists (who currently judge religious belief to be irrational) to revise their view of the rationality of religious belief. And I haven't seen any reason to think that's the case.
Moreover, I don't think we need to rely on the indirect evidence of "expert testimony" here, since the first-order arguments are fairly straightforward to assess. Cosmological and fine-tuning arguments don't support anything stronger than minimal deism. The ontological argument is obvious sophistry, and the modal version is question-begging. The design argument was defeated by Darwin; in its place we have the problems of evil and divine silence: the world just doesn't look anything like we'd expect it to if overseen by an omni-max god. In short, it seems to me, we seem to have every reason to reject theism, and no good reason to accept it.
Things get worse when we bundle in the quirky historical and theological claims of particular world religions. We know, from the fact that at best all but one of them is false, that holy texts are not in general reliable sources of evidence. Moreover, the particular contents put forth are often bizarre enough (fitting poorly with everything else we know of the world) to cast yet further doubt on them. Much of Christian theology (original sin, eternal damnation for honest non-believers, etc.) seems not just bizarre but patently immoral. It doesn't seem like the kind of thing someone could end up believing as the result of a careful and unbiased assessment of the evidence.
(Am I missing something? Feel free to comment with a brief explanation, if you think so.)
Of course, even if religious belief is epistemically unwarranted, that doesn't mark it out as warranting any special censure -- we humans are often unreasonable in all sorts of ways, mostly harmless, that aren't worth making a fuss about. But when religion is used as grounds for promoting a morally misguided social agenda, its lack of justification may become more important to note.