Here’s a thing I learned from my genetics teacher
First remember that eugenics is a bullshit movement designed at improving the genetic composition of the human race. Famous eugenics supporters include Hitler, Churchill, Keller, and arguably the current US President.
Okay now to my real point- if you are ever arguing with a eugenicist, you can tell them that they aren’t just morally fucked up but are also scientifically wrong.
This is because a lot of so called ‘undesirable genes’ are caused by recessive alleles (’versions of the gene’)- thus even if you eliminate those who have the undesirable trait, the huge majority of those recessive alleles will actually be held by people who are heterozygotes.
These heterozygotes will have one copy/allele of the ‘good’ gene and one copy/allele of the ‘bad’ gene. Because the ‘bad’ gene is recessive, the ‘good’ gene is the one that will be expressed, so these people won’t have the ‘undesirable’ trait.
The takeaway from this is that even if you eliminate the people who do express the ‘undesirable’ trait, there will be thousands of heterozygotes left, and if those heterozygotes have children together, they have a 1/4 chance of them both passing on their ‘bad’ allele and having a kid with the ‘bad’ or ‘undesirable’ trait.
So now really in conclusion, you would need to murder a HUGE percentage of the population: affected individuals and carrier heterozygotes in order to eliminate a simple trait from an entire population. THIS IS MORALLY WRONG for so many reasons but also it’s just fucking inefficient, so double whammy, especially if they don’t agree with the morally wrong part. ;) go forth and conquer, my children!