Like, best case scenario, a soldier in that war could come out with only minor hearing loss. How could the Germans justify hatred of anyone who was not in a great physical shape, with no disability, with troops wounded in war?
Before other responses come in, you might be interested in the response by u/justcoffeok in a thread more closely related to the T4 Aktion itself and my response concerning the general treatment of the disabled people in Nazi Germany.