Long before Hitler came after the Jews, he purged German society of genetic accidents, the retarded, the insane, the crippled, and the disabled WWI vets. The German "Nuremburg codes" were modeled on Virginia's eugenics legislation, but the german medical association went beyond involuntary sterilization. The name of the game was getting rid of "useless eaters," so that the "good" people, the "right" people, could live better.
1920 A jurist, Professor Binding, and a psychiatrist, Professor Hoche, publish the book, Die Freigabe der Vernichtung lebensunwerten Lebens (The sanctioning of the destruction of lives unworthy of being lived). (Science)
http://www.humanitas-international.org/holocaust/1920tbse.htm