I forgot that one of the main purposes of this blog was to keep a running link-record of the more interesting arguments I get into online, and likewise forgot to include this conversation.
The gist of my view was this: the probable truth of atheism and materialism does not provide an objective moral or rational reason to reject theism and non-materialism, at least not in and of itself. On atheism and materialism, you don't have any moral duties to consider beyond personal whim and 'gee, those people over there will beat the shit out of me if I don't do as they say.' Likewise, there are no rational 'oughts' in play beyond the same considerations. So we're in the position where a person who comes to believe that atheism and materialism is likely true still is lacking a reason to sustain that belief, because sustaining a belief - or believing itself - is just one more act to which such restraints don't apply. Would they rather believe that theism and non-materialism are more likely true? Then there's no real intellectual barrier preventing them from doing exactly that.
What I found interesting in the argument was this weird attempt by the resident materialist atheists to try and find some kind, any kind, of restraint for the hypothetical theist who believes atheism and materialism are likely true, but who perseveres in their belief all the same (and, horror of horrors, urges others to do so as well.) But what's fascinating is that even granting the likely truth of atheism and materialism still doesn't give a person a reason to abandon their faith, because a world where both were true would be a world where all the intellectual rules we're used to living by (and have largely inherited from distinctly non-materialist, theistic ancestors) are only in force if we damn well want them to be. When you're left with a metaphysical view that only leaves force and whim as the real deciders of what 'oughts' there are, the metaphysical view itself is open to be sacrificed.
This isn't a novel view on my part - I've seen others mention it before, in particular a Christian quantum chemist (I think) whose name I forget. But it does seem like a view that's worth promoting more, though it has to be done with care - arguments like these are touchy, because they're easy to misinterpret. Also because, I think, a lot of Christians try to play the 'accentuate the positive' game with atheists, and have largely sacrificed the idea that metaphysical views like atheist materialism have a serious (much less negative, even from the point of view of a Christian) impact on our intellectual lives. We can't seriously suggest that thinking about things and coming to the proper conclusions may well be necessary to live morally and do the right thing, can we? How prideful.