someone's usually taking their crazy pills when inciting such hatred instead of following the more positive ideas preached in their holy books and whatnot.
They're not, though. I spent twenty years of my life in the fold and have seen too much of this firsthand. I've done it myself. The vast majority of the time, no crazy pills are involved. We're talking about ordinary people you'd never look twice at who suddenly turn batshit crazy when certain topics come up.
Here's an example (which illustrates the critical-thought-killing aspects rather than the tribal ones): My physics professor in college was a Christian fundamentalist. I liked him, he was smart, knew his physics, liked to play the guitar. One day in class we were talking about electrical fields and going over the equations that describe the field's strength as a function of distance from a point charge. He noted that the equation was related to the one for the surface area of the sphere, and suddenly went into what I can only describe as a fit of ecstasy. His voice quivered, his head inclined upwards; his whole body practically shook, and he started talking about how the mind of God can be seen everywhere. It didn't seem to occur to him that whatever the stuff of electromagnetism is, it would have to "spread out" as the surface of a sphere as it "moved away from" the point charge, and so of course that's what the equation would look like. It was one of the weirdest things I've ever seen.
But harmless, right? I also discovered later that the guy is a big ID crusader, probably as a result of the same type of thinking.