Eugenics is open and fine so long as you just call it "sexual preference" and aren't physically sterilising people. The sterilising has to be social and cultural rather than physical. Think about the "Incel" thing. Those guys have effectively been sterilised and society at large is just fine with it.

Why do you think people are getting taller all the time? It's not just access to food. Women, who have complete control over reproduction, are attracted to taller men and subconsciously work to breed shorter men out of existence. That's just one example among many. Humans are eugenecists by nature, especially women since they tend to hold higher standards when looking for a mate and have full control of reproduction. If women don't think you're fit to breed, you won't, and your genes will be out of the gene pool.

This stuff is just a simple fact of life which people like to ignore. It gets darker when you realise that media also influences attraction, which gives the people who control the media to literally influence and control the human gene pool.