"I never considered a difference of opinion in politics, in religion, in philosophy, as cause for withdrawing from a friend. " - Thomas Jefferson
Unfortunately, the Us vs. THEM mentality seems to be propagating more and more these days. "Divide and Conquer" isn't just a military strategy. It's a highly successful way for keeping a population from moving forward in many ways. I live in the DC metro area and have seen a "Democrats need not apply" sign up in a store front. I think it was meant to be humorous, but it's still fairly screwed up.
"Disliking or hating something conditions you to (1) ignore virtues in the disliked, (2) dislike people, products, and actions associated with the disliked, and (3) distort other facts to facilitate hatred.
Startups should focus on their customers, not their competition—whom they may dislike." -This is #3 on VentureHacks cheat sheet of point from "The Psychology of Entrepreneurial Misjudgment"