I'm sure the ad is real, although I don't know it for a fact. It is still a real organization, though the name changed 30ish years ago. It was between 10 and 15 years ago that Obama signed Rosa's law, changing the words in federal law to "mental disability" or "an individual with an intellectual disability".

Remember, there was a time when that wasn't a pejorative term. It was a diagnosis. The way people used the word to "other" those with disabilities is what made it pejorative. Prior to that it was a neutral term.

A lot of terms used to make fun of intelligence used to be a diagnosis, like idiot and imbecile. That's really neither here nor there, but I find it interesting how mental medical diagnoses become insults but physical ones don't. I've never had someone yell "you play baseball like a paraplegic!" at me.

Edit: I was wrong and have been corrected. See below.