They absolutely are wrong from a scientific perspective.

Quick sidetrack: There’s a lot of misunderstanding about what people of the time meant by eugenics, because it’s rightly been associated with Nazis. That’s just where eugenics inevitably winds up, and it can’t and shouldn’t be uncoupled from that history. But prior to that it was considered a progressive cause, because the ideal was to reduce or eliminate human suffering by stopping disabled people, criminals, and other people considered undesirable from having children and thus preventing more disabled people, criminals, etc from being born to begin with.

But that’s not how genetics or criminality works. Most disabled people aren’t born with their disabilities, and those that are aren’t necessarily inherited from their parents; with deaf people for example, the vast majority have two hearing parents and they’re deaf due to a de novo mutation. If no deaf person has children ever again you would still have roughly the same number of deaf people in the world.

In addition from a genetics perspective, eliminating a trait from the gene pool can have weird, unexpected effects downstream. Maybe once you remove a lot of these things you think are undesirable at the same time, it causes a collapse of something else you didn’t even know was related.