Why is it some people hate people cause their race?

Fear and ignorance. Things that we would do well to remember that all of us are susceptible to. 

They were taught to. 

if you mean

why are people against diversity?

then, why not?

They are just ignorant and intolerant people towards difference in others. Racist people are problematic in the world and they are pathetic human beings.

It's called Tribalism. People do that naturally, but with education and some compunction they learn to get out of it because it's irrational, and I can even say, unscientific. Science was attempting to prove something called "racialism" in the not too distant past. The scientific community found that it was all wrong, and disproved it. They dropped it, and the racists in society took it up and are currently using it to Race bait, to create more tribalism, which divides the country irrationally. We are all Homo sapiens, scientifically speaking. 

Joe Biden Saying The N Word

https://www.youtube.com/watch?v=Lg83z7lxZMc