Earlier quoted context omitted.
Why is it so hard to imagine that maybe there are meaningful group variations within the human species? The worst things humans have ever done to each other have all centered around the notion of "meaningful group variations within the human species". Without hard science, it's a scary and dangerous place.
I was under the impression that communism was centered around the notion that people are all equal and highly malleable, not that there were intrinsic and immutable differences between human groups. But assuming you are actually referring to nationalists (who probably rank #2 on the list of "worst things humans have done to each other"), I'll just quote a blog post Bryan Caplan wrote today: We've learned so much from…
If you think that communism is worse, that's fine by me. It doesn't change the fact that history is littered with cautionary examples of group-based determinism gone terribly wrong. It's naive to pretend otherwise.