Hitler singled out anyone that did not conform to his ideas of racial purity. To join the SS, the applicant had to show a family genealogy that stretched back far enough to show his blood was “pure.” I watched a wartime news reel that showed German scientists measuring the head of a sub-human or untermensch with calipers.
The Nazi program to sterilize those deemed unfit had its roots in similar actions taking place in the United States.
“Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man. It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man himself, hardly any one is so ignorant as to allow his worst animals to breed (Darwin, 1871, 1896, p. 133-134).”
Racial purity was not just a Nazi idea.
And further commentary on Pope Pius XII by Rabbi Dalin: