Anti-natalists can have a variety of rationales for their choices -- a belief that one has an ethical obligation to not bring children into the world being one of them, is not the same as the belief in a class of people that should neither procreate or be eradicated. One is megalomaniacal.

That's not even touching the absurdities baked into the idea of "improvements." Superiority is very much a subjective evaluation. Genetic fitness isn't the same as one culture's preferential vision of what it considers a superior human being.