South Park has always been fundamentally reactionary; those pushing for change are wrong no matter what change they push for. Nothing is a bigger crime to Matt and Trey than Giving a Shit. Their ideology is apathetic-libertarian; whether you're on the left or the right, if you're asking me to change my behavior, you suck.
As it stands, the political left tends to push for more change than the political right does; as it stands, Matt and Trey admit they dislike conservatives and "really fucking hate" liberals. It isn't about left or right; it's about change versus comfort. If you're trying to change something, they think you're annoying. And they think you're lame, because caring about stuff is lame.
It's the same attitude that establishes "u mad" and "butthurt" as the ultimate trump cards in internet arguments: caring is for losers, and if you become personally invested in politics you're part of the problem. Uncritical, detached acceptance of the status quo is the only morally upright posture, and those who draw a distinction between is and ought are all smug bullies, outlandish freaks, and/or closed-minded zealots.
It's a show that teaches its audience to become lazy and self-satisfied, that praises them for being uncritically accepting of their own biases, and that provides them with an endless buffet of thought-terminating cliches suitable for shutting down all manner of challenges to their comfort zones.
South Park is a place where you never have to have your assumptions challenged. It's a place where you're always right, you shouldn't bother to think, and the people asking you to change your mind are annoying busybodies and prigs who should just shut up and leave you alone.
South Park is, if you'll excuse the expression...a "safe space."