Dating & Mating is eugenics at a conscious & subconscious level.
By the same logic, there is nothing wrong with censorship, because individuals also decide to not say certain things or not pay attention to certain things.
Is bemoaning the fertility of some disfavoured social or religious group eugenicist? If it is then a hell of a lot of people are eugenicist, and definitely not confined to the right.
You can see this effect in a short scale too. J. K. Rowling was once considered a feminist and role figure for an accomplished woman, until her views on trans people made her no longer reflect the progressive opinions of today.
I think this is part of the normal progression of modern society, accelerated by the ability to reach out to countless people across the world.
It's interesting and perhaps a little scary to theorise what taboos will change from "disgusting" to "progressive" in the future. There's a good chance most people, even the progressive ones, will fall behind on the curve of acceptance at some point.
I myself believe that eugenics, if applied well, can help humanity. In practice, though, I don't think humanity can be trusted to apply it well, so any attempt to introduce it is doomed to be plagued by humanity's flaws. It's the same reason communism fails: humanity cannot work together enough to make something work that in theory would be beneficial to all of us.