These days, 'racism' is about culture, not "race" in the sense of skin pigmentation or skull shape. We know anyway, that "race", technically speaking, is meaningless in humans.
It could be said that appearance (okay, 'race') is a really crappy proxy for culture, and people choose to discriminate and abuse others on the basis of culture.
By way of example, hardworking, moral, aspirational Hindus and Sikhs are well-liked where I live. Yet, their genetically identical south-Asian radical Muslim kin are despised and shunned, and are dirt-poor as a result. Discriminating against somebody on the basis of a dubious socially-conditioned trait like adherence to conservative Islam (say) would be impossible to do through genetic data alone.
As it were, the worst-behaved and most aggressive people I come across at street-level would be people who wear sleeveless puff jackets, have beards, shave the sides of their heads, drive BMWs, don't bathe, and show no respect to whites or women. Dress and behaviour -- not genetics.