This is a response I put up on Debunking Christianity:
It could be, though, that two people who are pursuing the truth as best they can, being as reasonable as it is possible for a human being to be, come to different answers without there by any irrationality on anyone's part. It is only that different life-experiences, different intellectual contacts, etc. etc., lead to different results. One side has to be mistaken, but neither side has to be irrational. One of them is correct, the other is in error, but neither is irrational. That is the presumption that I like to use in discussion with opponents. Of course, there's all sorts of crap going on in our minds when we try to think, but all we can ask of one another is that we do our best. But then, the title of my site isn't Debunking Atheism.
Do people who believed in the oxygen theory have to explain away all the people who believed in phlogiston?
Explaining the other side psychologically doesn't do anything. Both sides can do it, all day long, to one another. If I think you didn't discover the truth, then I can explain why you didn't. If I didn't discover the truth, then you can explain me away, too.
What you try to do in response to believers is to get them to grant that you may have seen something that they have overlooked. Why can't you accept the possibility that some Christian has seen something that you have overlooked?