I thought Bananarama hit on what I mostly just scraped on, that there is individual racism and systematic racism. Sure, you can have one black person dislike a person for being white, but systematic racism goes deeper. The history of minority suppression runs deep within America, and back then, you had all different ways to lower them in society. You had Jim Crow, "separate yet equal", Grandfather clause, poll tax, among countless other ways to subjugate blacks. There are similar and different ways other races have been treated. With what bobjr. was saying, the Irish were treated so poorly, that they were called white (n-word). It is a horrible aspect of culture, but we must do our best to be better than what history has shown.
Moreover, some of my very recent ancestors who were just horrible people, and the rest of my family distanced from them. I also live in a Southern state, and I had ancestors fight in the Confederate Army, which fought on ill-faith. Apart from that, Southern education can sometimes be wishy-washy about how they talk about the Civil War. You have the question, "Why did the South fight for in the Civil War?" and you sometimes get, "states rights" or "economic hardship". I think we should just admit the fault of Southern Confederates and move on.