I will start this statement with this;
When the slaves were freed, do you think that the racist slave owners suddenly saw their former slaves as people with the new law change?  Do you think the slaves just instantly let go of their resentment of their former owners and others like them?
The answer is a solid and resounding, “NO!”
Their only way to cope with the sudden idea that their slaves were actually people was to think of them as their own race. And they, in turn, taught their children their way of “not being racist”.
On the other side, the slaves learned to hate their owners and that doesn’t just disappear overnight either. They probably taught their children similar tactics to cope with the new laws as well.
It’s been less than a century since the Civil Rights Movement and less than a century before that, the slaves were freed.
I’m not condoning the practice of what I call “softcore racism”. I’m simply saying, it takes time to weed out that kind of mentality with tolerance and education. The people who don’t know they’re racist honestly don’t know they are and need to understand that they’ve simply been taught by their parents (who were taught by their parents and so on) to think a certain way and it’s not entirely their fault.
And I’m not naming any specific races because A LOT of people of my race are racist as all hell and I’ve seen it in other races(besides white) as well and it ALL needs to stop. But we can only combat it with patience, understanding and education.