Eugenics has become a word that everyone must decry as false or be shouted down.
But the truth is that a form of eugenics has been practiced long before Darwin came along. Ancient peoples probably noticed that when close blood relatives had children they suffered deformities far more often than offspring from non-relatives. Of course they didn't understand about genes so they quite reasonably attributed the deformities to a divine curse or similar and made religious edicts preventing such mating. To this day most societies disapprove of brothers and sisters etc. having children.
Whilst evolution is primarily guided by natural selection, unnatural selection (say, dog breeders) can also force species to evolve along a different path than they otherwise might have done. This is as true of humans as it is of dogs. Don't get sentimental that we are biologically different. Just because monsters like Hitler went to the extremes of terrifying brutality does not make human eugenics automatically untrue or inherently evil. The ancient custom of preventing close relatives from mating is a mild mannered form of eugenics that benefits us all by preventing potentially dangerous recessive genes from becoming dominant (or preventing Thor's/Jehooby's curse if you prefer).
Preventing brother/sister matings is unnnatural, human guided selection at work - i.e. eugenics. Although you can mate with almost anyone in the world of the opposite sex you can't mate legally with everyone. This is controlled selective breeding, though of course in its mildest possible form.
And like most things (like the answers I no doubt will get), it can be taken to extremes.