How about the fact that it's the equivalent of smashing rocks together to make fire rather than using a box of matches or a lighter?

We will breed the Ubermenschen!
...by rolling nature's dice until we get a bunch of highly inbred blondeyblues.

Nowadays we can just do things like selecting an embryo that isn't going to be born with a horrible disease and promptly die, I imagine when the public gets their knickers out of a twist we'll be able to start splicing genes into human embryos rather than just firing gametes together until something desirable sticks.

Eugenics is the primitive forefather to genetic engineering, so whilst muh feels applies to the luddites who think that the apocalypse will be unleashed when we make glow in the dark humanoids for eugenics it's just because it's outdated.