The first topic this article brings up is incest, with an example of a brother & sister couple who had several congenitally diseased children.

It is worth noting that those parents were not banned from having children altogether, they were just prohibited from having children with each other. They could have each found other partners and had children with those other hypothetical partners, and there wouldn’t have been an issue. Usually “eugenics” refers to policies that prevent certain individuals from procreating with any partner, like forced sterilization.

Also, this article is kind of similar to a disingenuous argument about abortion that conservatives sometimes make.

Disingenuous pro-life conservatives: “allowing women to get abortions is eugenics against whichever women end up doing so (i.e. largely black women), therefore Democrats are racist and abortion should be illegal”

Effective Altruism weirdos: “allowing women to get abortions is eugenics against whichever women end up doing so (i.e. women who become pregnant with deformed embryos), therefore eugenics isn’t that bad”

Both start with the same wrongheaded idea, but they use different examples to draw converse conclusions from it.