I'm prompted by this post of Ophelia Benson's, at Butterflies and Wheels, to report on some relevant experience of my own. I've been an atheist ever since I began seriously to think about religion, and I wasn't any kind of believer before that either, not having had a religious upbringing. I remember having arguments about the existence or otherwise of God in my last year or two at school (that's high school, not college), but since then, in adult life, I've had very few discussions of this kind. Naturally, I have friends and acquaintances who are religious, and though I don't share their beliefs, I respect not only their right to those beliefs but also what I imagine to be some of the grounds, or at least impulses, supporting or informing them. Also, when I started reading intensively in the literature of the Holocaust some ten years ago, I read a certain amount of Holocaust theology and through that I came to see how problems posed within a theological frame of reference can have strong parallels with moral or other questions within a secular one.
Twice during recent years I tried to engage people I know well, and whom I also like and respect, in a discussion about religion - this with a view, not to challenging their beliefs, but to trying to see if my own assumptions about the way in which they held them were even half-way right. Both conversations ran, pretty well immediately, into the ground. In one, the answer to my very first question, asking for the basis of a friend's religious beliefs, was met by her with a polite but ultra-brief response, which made it clear that this wasn't a line of discussion she wanted to pursue further. On the other occasion, I asked a question of another friend in reaction to something he had casually volunteered about his (religiously-based) causal beliefs. His response produced an early impasse between us, in that it just made no sense except if you already held the belief it was supposed to provide evidence for.
I don't report this as proving that all conversations between the religious and the irreligious must go the same way. I hope not, in fact. My own reason for embarking on these two conversations was to explore what levels of mutual understanding are possible across the boundary that divides religious belief from atheism. But that is my limited, and so far unsuccessful, experience.