I think part of the US vs THEM mindset comes from our childhoods as well. Every kid out there learned to sort. First by color. Then by shape. Eventually getting down to the nuances of Cool Kids vs Geeks. We are trained to sort the world into categories. And yes, I agree — likely it all started back in the days when we had to sort out intense survival situations.

Friend? Foe? Predator? Dinner?

But then, I’m the woman who traps spiders in glasses & bits of cardboard & then releases them to the outdoors. :)