How is this not eugenics?
People making individual choices which respect the rights of others, with eugenics being part of their motivation, seems not really a bad thing?
Like, if there’s some recessive trait that someone has and wants this trait to continue to be expressed in the population, and they are maybe a bit confused about genetics, and so they take “does this person have this trait” as a factor in deciding who to date, I don’t think that’s a problem?
The problem is when either there is a large societal program trying to implement a specific eugenics plan, or when people use violence or coercion to try to achieve eugenics goals.
Some genes are better to have around than others, and it isn’t so much an issue to promote better ones on a small scale, but due to the risk of being wrong about what genes or qualities are better, it is probably a bad thing for it to be attempted (even if done non-coercively) on a large scale.
I guess another part of that is, on a large enough scale, it is difficult for any such thing to avoid being at least slightly coercive. If you give everyone who acts within some guidelines a reward, then withholding that reward from a small minority who don’t act within those guidelines, could be regarded as a punishment.
When individuals choose their own mates it's just called dating.
Because it's not supposed to improve the breed. However bizarre, it's merely a personal choice.