Go to minute 37 of this video interview of Daniel Dennett (featured on Edge.org). I found this to be an extremely well-reasoned inquiry into the systematically and intensely hypocritical web in which many doubting clergy feel trapped. Dennett suggests that the religion industry feel bound by a religious version of the Hippocratic Oath. He speaks of the felt need of preachers to weave their teachings somewhere between literalism and metaphor, never daring to land on one or the other for fear of angering huge swaths of the flock (though I do suspect that most believers are conflicted in that they themselves harbor both of these cravings).

[W]e've spread out and looked at a few more, and we've also started looking at seminary professors, the people that teach the pastors what they learn and often are instrumental in starting them down the path of this sort of systematic hypocrisy where they learn in seminary that there's what you can talk about in the seminary, and there's what you can say from the pulpit, and those are two different things. I think that this phenomenon of systematic hypocrisy is very serious. It is the structural problem in religion today, and churches deal with it in various ways, none of them very good. The reason they can't deal with them well is they have a principle, which is a little bit like the Hippocratic oath of medicine. First, do no harm. Well, they learn this, and they learn that from the pulpit the one thing they mustn't do is shake anybody's faith. If they've got a parish full of literalists, young earth ceationists, literal Bible believers who believe that all the miracles in the Bible really happened, and that the resurrection is the literal truth and all that, they must not disillusion those people. But then they also realize that a lot of other parishioners are not so sure; they think it's all sort of metaphor. Symbolic, yes, but they don't take it literally true. How do they thread the needle so that they don't offend the sophisticates in their congregation by insisting on the literal truth of the book of Genesis, let's say, while still not scaring, betraying, pulling the rug out from under the more naïve and literal-minded of their parishioners? There's no good solution to that problem as far as we can see, since they have this unspoken rule that they should not upset, undo, subvert the faith of anybody in the church. This means that there's a sort of enforced hypocrisy where the pastors speak from the pulpit quite literally, and if you weren't listening very carefully, you’d think: oh my gosh, this person really believes all this stuff. But they're putting in just enough hints for the sophisticates in the congregation so that the sophisticates are supposed to understand: Oh, no. This is all just symbolic. This is all just metaphorical. And that's the way they want it, but of course, they could never admit it. You couldn't put a little neon sign up over the pulpit that says, "Just metaphor, folks, just metaphor." It would destroy the whole thing. You can't admit that it's just metaphor even when you insist when anybody asks that it's just metaphor, and so this professional doubletalk persists, and if you study it for a while the way Linda and I have been doing, you come to realize that's what it is, and that means they've lost track of what it means to tell the truth. Oh, there are so many different kinds of truth. Here's where postmodernism comes back to haunt us. What a pernicious bit of intellectual vandalism that movement was! It gives license to this pernicious sort of lazy relativism.