I've never been called that before! My day is complete!
Are you claiming that tribalism doesn't exist? I'm not sure if that's what you're claiming..
But, long long before there were several billion of us on this "rock", we were killing each other, no?
Now that's not to say that there are not good folks around either, and also I actually made no claims that "differences" automatically meant "death" now did I, honey buns?
Rather, what I mean is that it's a basic part of the human psyche to view things in an "us and them" fashion. Take a look around you, do you not see it? One would have to be blind not to - black vs white, liberal vs conservative, Islam vs Judaism, Yankees vs Red Sox, Fender Jazz players vs Precision Bass players, etc etc etc.
Some kill for those differences, some simply argue, some don't feel strongly enough to even comment, some even celebrate those differences perhaps, but that aspect - 'us vs them" is a basic human component regardless is it not?