If you "believe" in behavioral evolutionary psychology, then racism can be explained quite simply:
Humans are a social animal, with evolved group behaviors. Part of that group behavior is inclusion/exclusion based on shared characteristics. The easiest way for humans to do that is to evolve instinctive distrust to those whose phenotype and genetic makeup is most dissimilar to their "in group", and to evolve instinctive trust to those who match us in appearance (language, culture, etc).
It's an evolutionary "shortcut", a pattern matching heuristic that served well in times when a tribe removed enough to look different was probably very dangerous. As any heuristic it had very rough applicability in a man-eat-man world.
Today, it is a mental handicap. As a heuristic it is wrong most of the time. As a cultural practice it is abhorrent. Yet, as an instinctive reaction has been scientifically shown to exist in almost all people in some measure, through minute timing differences in association tests. We all do it, only some of us try to be aware of it in order to rationally dismiss and remove the bias from our actions. Others are either oblivious, or thrive in the feeling of "common purpose" that group inclusion/exclusion dynamics offer.
The same dynamic applies to race, religion, gender, disability, sexual orientation, accent, economic class (visible), health, age and many other recognizable characteristics. Basically, anything you can identify in a person to separate into "us" and "other", at a glance, will be a focus of such biased thinking.
tl;dr: we are not that much more enlightened than monkeys.
Personally I don't doubt that 'sociobiology' is a significant factor in a lot of our behaviors. It makes enough sense that I would be surprised to not see it expressed. I see organized sports, and being a fan of sports teams, as being a direct expression of this principle. And of course 'nationalism'.
Related to the OP, I am negative about 'Zionists'. And any racist right-wing political party which most certainly includes Likud. That is sometimes mistaken for 'anti-semitism' I guess. Oh well. I suspect that there are probably more non-Jew Zionists than there are Jewish ones. And I find it questionable whether there really is much genetic material carried forward from the Judea of antiquity into the modern Ashkenazi populations anyway. Probably studies have been done about it, but I've not bothered to look for them.