Well as some said it has to do with their religious texts although they follow it very hypocritically following some and not following others. Or simply making stuff up off the spot (hell being a place of torture anyone haha... in the bible it's described as the grave and that's it).
Really I don't know why religions can be unaccepting. Really it turns out to be a lot of other things where they try to identify what am I and where do I belong which is a typical question in a social human world. In that process they also try to understand who isn't one of us which causes such things. Though for these people, they need not worry. In most of the religions they'll all be judged on the final days and then it'll only be up to god.
But you see this kind of thing in politics a lot. Hell a lot of the issues in American politics right now is based upon that notion (what does it mean to be an American and more importantly what isn't American). Whole tea party movement is based off this in fact of trying to figure out what America is and what doesn't belong (and on the more racial fronts of it, who doesn't belong). And despite one being religious and the other being political, I think they have similar connections just because humans are always trying to find their place in a social world. As much as we like individuality, we do seem to be social creatures. That is the reason Aristotle called Political science the master science, because it is the study of the social human.
