Nazi Logic

Abnormals and Mutants should not be seen by Normal People.
(This was not much in dispute for at least a hundred years.)

So they, whether hare-lipped or stammerers,
with Down's Syndrome or Cerebral Palsy,
must be locked away from sight.

Keeping one of these in an institution
costs as much as training a soldier.
So it is best to get rid of them altogether,
by or after performing Useful Experiments on them.

Those Useful Experiments informed modern psychiatry,
and most of the experimenters became respectable citizens
in the USA as well as Germany.