Then mock them for doing something stupid, not because you got it in your head that they have some kind of actual birth defect. Besides, when you say that it's the same as calling someone a retard in the 80's, you're tacitly admitting that these people aren't actually autistic, you're just calling them that because "retard" is out of vogue now and the current meme is "autist." Go figure.

Also, you listed the two things using parallel structure to pretty much directly imply they're very similar, so to say you're not saying one equals the other is pretty specious to me.