You aren’t wrong that there is/was a group of people that consider themselves South Park Conservative but the creators reject the notion that South Park is specifically liberal or conservative, because their intent is to parody any people they can. The creators dislike political correctness but they also dislike the forceful nature of conservatives applying their beliefs on other people. Read the South Park wikipedia page, it explains it pretty well.
Insinuating that South Park conservatives evolved into the alt-right is doing a lot of heavy lifting. Trey and Matt didn’t invent disliking political correctness.
I concur with this take. Like many facets of culture, some people/groups will project what they want onto a given cultural entity (South Park, in this case), but that doesn’t mean one should assume they speak for it.
For example, the “men’s rights activists” group appropriated the idea of “the red pill” from The Matrix. They certainly differ wildly in worldview from the Wachowski siblings.
(I say this in the friendly spirit of a long-defeated fellow pedant who has hit people with your exact comment for decades)