The principles of eugenics cannot be successfully argued against. Humans, being animals, can potentially be bred for desirable traits, or be bred to get rid of undesirable traits. That is just a fact.
Recent quite good science, as opposed to the crappy eugenic “science” of 1900 or so, seems to indicate that intelligence (whatever that means) is something between 1/3 and 2/3 heritable. Since in modern societies we have efficient assortative mating, and the intelligent and successful have a much lower birth rate, we are by definition breeding for lower average intelligence over time.
The problem with doing anything about this, of course, is implementation. No human or organization, IMO, is wise enough or good enough to be decide what the desirable and undesirable traits are, and certainly not to be entrusted with the power necessary to effectively control human reproduction.
So we’ll just have to remain wild animals and hope for the best.
No, none of that is fact. Eugenics is one of the most anti-family doctrines that ever came to be; it led directly to Adolf. Relating intelligence to so-called “eugenics” is to deny God.