Their reasons are, invalid, and irrational , and irrelevant, in modern society. There be coming a smaller minority, year by year, as our children are starting to think for themselves. We will evolve, to a better world. It's a slow progression.
Quite often they have no idea that they are racist. I'm guessing there's not a connection between thinking you are better than somebody else and racism . I grew up in a predominately white part of the country . I'm sure I heard a lot of claims indicating that someone was better than someone else, in so many words at least. These were Irish, Scottish, Welch,Italian every ethnicity but no African , Asian , or Indian Americans. We just didn't have an opportunity to use racism as a reason to be stuck up. We all LOOKED kind of similar .
Some people think they are better than everyone else. This doesn't necessarily have to be racist, it can be but doesn't have to be. Usually this person is narrow minded an has a a higher opinion of themselves than anybody else does. In short, he or she is your basic A-hole!!