I would suggest the eugenicists often follow in the wake of the hateful and what you're seeing is a post-hoc rationalisation of pre-existing feelings. Eugenics, by the nature of what it does, dehumanises 'the other' but its cold and calculating pseudo-science approach doesn't make it less hateful. It simply makes it far more likely to spring up in the wake of a malevolent leader - and there is nothing more terrifying than a middle-class psychopath in a position of scientific authority.