Just reminding everyone of one more sad thing—every good cause to rally people under generally needs an enemy. And if there isnt one, it usually develops or is found. People somehow just want to be against things rather than for them..
Also, atheism seems to be one of the few things most of us here have in common so Matt Newports post hits a nail there. We have a tradition of bashing theism. Traditions go a long way towards cementing a sense of community, so they do have a positive side. But the fact is that once a tradition has developed, people who break it are usually viewed as outsiders in some sense so it makes sense for people to stick to the traditons.