Hitch talks about debating religious people:
Usually, when I ask some Calvinist whether he is really a Calvinist (in the sense, say, of believing that I will end up in hell), there is a slight reluctance to say yes, and a slight wince from his congregation. I have come to the conclusion that this has something to do with the justly famed tradition of Southern hospitality: You can't very easily invite somebody to your church and then to supper and inform him that he's marked for perdition.
More to the point, though, you soon discover that many of those attending are not so sure about all the doctrines, either, just as you very swiftly find out that a vast number of Catholics don't truly believe more than about half of what their church instructs them to think. Every now and then I read reports of polls that tell me that more Americans believe in the virgin birth or the devil than believe in Darwinism: I'd be pretty sure that at least some of these are unwilling to confess their doubts to someone who calls them up on their kitchen phone.