Yeah it's one of those things that in theory it could make sense, it could be. However since we are humans, there does not exist any way that would not be morally abhorrent to some group of people. There's zero way that in doing it this way wouldn't destroy x group of people. And that's why it can never be done. Eugenics is just too close to genocide.
It's an uncomfortable question, but a question that appears to be made in good faith and OP shouldn't be getting downvoted. I do not see the benefit of "burying" this question and the many well written answers in this thread show that.