Eugenics is not a policy proposal, it's an engineering discipline. Eugenics is the practice of using selective breeding to cause future generations to display desired genetic traits.

So, to be more precise in my language, the scientific fact is this: eugenics can be used to alter future genotypes (with high probability) and to alter phenotypes to the extent that phenotypes are caused by genetics.

> Eugenics is a policy proposal, not a fact. How could it possibly be part of the scientific consensus?

It was a proposal for dealing with some "facts" and "theories" about which there was scientific consensus.

BTW - Eugenics in the US was a progressive enterprise.