Race is not merely a social concept, though it has more of a social definition now than it used to due to the abundance of people with mixed heritage. The fact that it's primarily about pigmentation doesn't make it imaginary. "The race question", written for UNESCO originally in 1950, and serving an agenda of anti-racism, said that there was no basis for the idea of pure races, while talking about 3 actual races (apparently ignoring aboriginals of the New World and Australia). The fact that there is variation within any race doesn't make race imaginary; it just supplies us with an argument of the beard. And the same is true of languages and biological varieties.

I cannot figure out what the "no such thing as race" believers think the definition of race (or particular races) is. Sometimes they seem to confuse it with species, saying that since the human races can interbreed they're not races. In biology, varieties within a species are frequently recognized, and they can interbreed, but usually don't. Today, Thom claimed that race isn't real because it's not located in a single gene. Well, neither is schizophrenia, but schizophrenia is still a disease. Sometimes they claim that it's because pigmentation differences (which are not the only racial differences) arise from an evolutionary cause, in this case selection due to ultraviolet-light exposure. However, all the differences between varieties, species, genera, families, orders, classes, phyla and kingdoms are due to selection.

I think this push to convince everyone that there's no such thing as race is PC crap. You don't have to say that race doesn't exist in order to say that it shouldn't be used as an excuse to treat people differently. And the problem with saying race doesn't exist is that it would mean racism doesn't exist and that you can't commit genocide unless you kill the requisite percentage of the entire human species, and that police violence against black Americans is a coincidence.