Why are some people racist?

So I want to start off saying that I really dislike when people talk about other people because of race and color. Not all blacks are ghetto and thugs, not all whites are country and hillbillies, and not all Asians are shalion monks? So why judge people of color? Judge people for what they do. Because we are all humans we just have different cultures different voices and we make different choices, but we are all human. So let's stop fighting each other we should stop this. Thank you.