You have to remember that prior to WWII, the study of "Eugenics" was a well respected science. Eugenics was the comparative study of human races, which today would be labeled "racism". Prior to WWII, there was a lot of people comparing the size of people's heads to their score on IQ tests and comparing the IQ test results of different races of people; asian, negro, caucasian, mid-eastern and such. All of that kinda stuff would be considered "racist" today, and it's largely WWII that caused the comparative study of human races to be frowned upon. Nowadays, we're perfectly happy to compare the intelligence of dolphins to chimps and chimps to orangutans and even orangutans to certain birds, but no one wants to shine the light of science on the comparative study of human intelligence for fear of being labelled a racist and having their funding cut.

Nazi's considered mental illness as a genetic defect and therefore proof of inferiority, so that mental hospitals quietly exterminated their patients and attributed their deaths to heart attacks and strokes and the like.

I really don't know if defects at birth, like cleft palettes, hair lips or missing fingers or toes were something the Nazi's targeted as "genetic defects" worthy of extermination or not.

But, certainly, physical handicaps that arose after a person was born weren't considered "defects". A child who was disfigured after being kicked by a horse or a person who's hand was mutilated in a machine shop accident were considered "unlucky" rather than "inferior".