From reading of 19th century literature and history -- for example, I read that it was believed by people in the time of the "Elephant Man" that deformities were caused by bad deeds of parents (but also similar quality thinking that his mom had been scared by an elephant); anyway, people saw nothing wrong in handicapped people being exhibited and the movie Freaks made in the 1930s used performers from side shows which even in the 1960s existed in the USA although I think they were on their way out by then.
I have also had conversations with people born in the late 19th or early 20th century and based on these, it is my sense that it was a tougher time in general.
I wonder, assuming it is agreed that there has been a significant shift, what caused it and when? Could better health in general have reduced the number of people with handicaps so there was less "handicap fatigue?" Could Roosevelt's handicap have reduced the stigma? Was it a general increase in education level?