I feel your pain there, RW, and it's indeed a horrifying, tribalistic attribute of human nature. What's even worse, but plain and simple, is that it doesn't even depend on what grounds you belong to. The poison simply finds a way into people's hearts. And this poison is political in nature, not ethical nor moral, which makes it even more powerful and disgusting. And it will stay whether or not we have a religious nation or atheistic.
In one place you'll see witches being burned by Christian fanatics. In another you'll see a white guy kicking a black just for the heck of it. In another, it's Atheists bullying and beating a religious person, even if the latter did not intend any harm. We'll see females being oppressed by males, poor being used as ash-trays by the rich, modernists will treat traditionalists like shit, young people treating the elderly as disposable, artists being crushed under the feat of businessmen and lawmakers, and commoners having nowhere else to go.
So tell me: Why must we war because we see something the others cannot? Why can't we all just get along now? What makes someone more important than another?