But even that isn't really correct, right? It's definitely true that the racial categorizations chosen by the census aren't great at dividing up humanity by genetic distance; there is probably a lot of genetic diversity in some particular race, while other races deemed distinct are nearly genetically identical. (And obviously, all humans are exceedingly similar genetically on an absolute scale.) But the the census races aren't useless or random biologically. There are plenty of diseases which have higher prevalence in some races than others. Whites are more likely to get skin cancer, less likely to be lactose intolerant. Asians are more likely to get alcohol flush reaction. Blacks are the exclusive sufferers of sickle-cell disease.

If he wants to say "the races as defined by the census are only weakly correlated with genetic distance or geographic ancestry", then fine. But that's a far cry from "the 'race' categories that are used in the United States are arbitrary...and do not correspond to any scientific view of geographical populations."