Why our brain hates other people?

It is a very tricky question. We do hate other people ... without any reason sometimes. Let us understand why?

People generally tend to create two groups of the society Us/them based on gender, language, religion, social status and what not. This closed group "US" will have all our sympathies and regards without any reason and expectation. The other group "Them", in our opinion have all the flaws and do all the faulty things in the world, and by default our brain hates them.

This kind of dividing the world into Us and them is very deeply rooted in our mind and even proven to have an ancient evolutionary legacy. One more interesting factor is, it is very difficult to understand when a person from "Us" category will become "them" and vice versa. 

Across cultures and throughout history people who are categorized as "Us" will be viewed as more correct, wise, moral, and worthy. And of course, "them" are the different ones, who are viewed with cognitive particularity and cold heart.

These multiple dichotomies people create in their minds unknowingly and involuntarily is the reason why our brain hates other (them) people.