This is so disgusting. Why does religion cause so much bloodshed?
Humans spent millions of years as tribalistic/pack-orientated animals. Evolution doesn't rid people of those instincts.
We're still tribal, and will band together with others of similar beliefs (take football fandom, or political allegiances)
There's also the theory of the 'god gene', which makes [some/most] people predisposed to believing in some form of deity. And, in our tragically brief lives, the notion of there being somthing that comes after we (or our loved ones) die is an extremely seductive notion.
Throw a fervent belief in a deity and all the accompanying narrative in with the tribal mentality, and it's a toxic brew.
On the other hand, I do think even the most ardent religious believers have intellectual doubts. They'd never communicate these, but it does raise within them a sense of insecurity, especially when another person dismantles or mocks their whole belief foundation.
A more general point is I also suspect that, given most religions make a sin of hedonism and pleasure, the followrs of those religions despise the fact that others who don't believe are having all that fun when they, the believer, denies themselves. A huge resentment builds.
