Humans resist being killed. The worthy are better at resisting. While individual cases are confounded by luck, on average anything which kills humans will kill the unworthy preferentially.
P.S. BLM is eugenic.
I think the whole [cops are massacring minorities] thing was supposed to be taken as a command. Dog whistle. After all, every time they tell you how it's racist to think blacks are X or Y, blacks hear they're supposed to X or Y harder, just like they're supposed to. Sadly cops are middlish class and resist random violence, for some reason. Had the cops started wiping out blacks like they were told to, BLM probably would have been avoided.
Still, they're pulling rookie numbers compared to Stalin. Yes it's eugenic but it's hardly a strong effect at this level.