Make no mistake about it: the horrors of Hitler's AUSCHWITZ and AKTION T4 and der HUNGERPLAN were all birthed about the same time as Hitler himself: in the 1870s and 1880s as Social Darwinism captured the new science of BIOLOGY.
Nothing better captures how Hitler's gang regarded the small and weak, the useless mouths he sought to kill off to free up resources to defend the worthy from the evil, than the biological abortion-of-a-term, commensal.
The Communists and the Jews Hitler called germs, pathogens, parasites.
Notice the biological term used : parasite. Bad guys: fear.
Hitler called forth his Ayran race of Germans to be the hosts of New Order Europe. Good Guys, admire.
Another biological term.
But Romas, Poles, the handicapped : useless, neither helpful or harmful.
Useless one way or other: eliminate.
He did : tens of millions of them......