The tribe. It could be enforced at the local level, and/or elevated to a higher level. Also that artist was correct, it's just taboo to admit it.

How will you be handle being told that you're inferior and that you're not allowed to breed?

I don't mean that as an insult. I mean it as an inevitability.

Everyone who promotes eugenics always imagines themselves as being the superior one.

I would rather have a world where we strive to create the best of us, rather than rolling the dice with perpetuating hereditary diseases and leaving our future to blind luck.

To answer your question : If I were born with a horrific disease that has a significant chance to pass that down to the next generation, it would be my responsibility to not pass that down to the next generation. I would understand.

There are always superior people and inferior people depending on a multitude of variables : time, genetics, intelligence, environment, training, etc. Ignoring genetics as an essential pillar of this is irresponsible.

But if someone told you today, that you were not allowed to procreate, what would you do?

You do not have to hand it to the Nazis on Eugenics. Preventing the "wrong people" from breeding always seems to devolve to genocide.

Contraceptives prevent "the wrong people" from breeding, and is a form of Eugenics. Where is the resulting genocide?