The human animal is a social animal, and lives in families and groups, that keep themselves organized and together by some sort of ideology, of which the main operative content is usually that We are better than Them, and only fools or evil persons can disagree.

Possibly this part of the human zoological inheritance is unavoidable - it's similar with wolves, hyenas, chickens, goats ... - but rational human beings reject totalitarian ideas and attitudes, however based on beastly emotions. In any case, the normal human habit to think and believe in terms of We, and to discriminate, abuse, or persecute whomever is not like We are, has cost many hundreds of millions of human lives, so far.