The first three paragraphs of Atrios' What I Believe post describe my religious background almost perfectly. But, then he says this:

I'm puzzled why some religious people seem to get upset by more outspoken atheists. I can turn on the teevee and be threatened with damnation and hellfire. Who cares if Sam Harris thinks you're stupid? If atheists want to engage in their own brand of proselytizing, good for them. I'm not especially interested in it, but what's wrong with it? There are Christian missionaries all over the world.

Really, that's puzzling? The reason religious people get upset by outspoken atheists is because outspoken atheists insult, mock and belittle religious people and their beliefs (with good reason, IMO, but that's beside the point). And outspoken atheists scare some religious people because outspoken atheists want to spread their godless message - which results in everlasting torment for those who abandon faith - to religious people including, gasp, the children of the religious. If you're a Christian and you really believe Hell awaits non-believers, then you're probably going to worry if someone is trying to lead someone you care about down that path - you'll fight that message, because you're trying to 'save' your loved ones.

And obviously, there's that good-ol tribal defense thing, too - people will always defend their tribe against outsiders. And religion is the biggest tribe of them all.