I think there are a lot of people who have missed the idea of parody. South Park is not literally trying to tell you that Aspergers is a fake condition. (Though I'd also argue the autism spectrum is just that, a spectrum, and there's no reason to drag a Nazi's name into it.)
Read Randy's dialogue here:
"It's pretty sh***y when you work so hard to be a great parent, and then the "government" comes along and with one shot turns your child into a "mentally incapacitated" freak! I mean look at him. He's disinterested, depressed, self-loathing. It's most likely the reason his mother and I got divorced!"
The joke here, not counting the one about antivaxxers (Mr. Mackey "diagnoses" Stan with Aspergers just because he got the flu shot last year), is that parents do more to harm their child when they talk about the child like they're a disease.
When Stan finds out the Aspergers group is a fakeout, "Morpheus" tells him "If there was a social development disease, you wouldn't call it Asperger's! That's just, that's just mean!" And he's got a point. This is the commentary South Park is making about autism and Aspergers, not literally telling you it's fake or that everyone who has it is a freak. (I am all for inflammatory commentary about Hans Asperger.)
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god...it's brutal out here