Ok, so "black" or "White" are not absolutely clear labels that we can use to describe every single person ever. No shit... Still, Morgan Freeman is black and Margot Robbie is White, and I'm White because both my parents are White, and if there's a serial killer roaming the streets then knowing if he's "black" or "White" is very useful information so I know what to be on the lookout for, etc.
It's like those insufferable people who can't wait to point out that "A tomato is actually a fruit!" any time it comes up in conversation. Ok, so what? "Race is a social construct!" Ok, so what?