The above aren't "my words."
It's a fact that Stone is a registered Republican and that Parker is a registered Libretarian.
I enjoyed reading the interview you posted, but it's mainly just about the two episodes they did about the network refusing to air a cartoon with Mohammed in it.
In an interview in the March 13, 2006 Time magazine, the two stated that the only reason people might peg them for conservatives is that they are willing to mock anti-smoking laws and hippies. They also stated that the show could just as easily be pegged as a show supporting liberal ideologies. The interview ended with Parker quipping, "We still believe that all people are born bad and are made good by society, rather than the opposite", and Stone adding, "Actually, I think that's where we're conservative".
Actually, I think that's where Trey's quite religious, truth be told...nice job at damage control, though.
How is a South Park written?
My long-standing hypothesis is that like many TV comedy writers of the last ten years or so, they get high and watch The Simpsons, then expand on a few of the many-layered jokes of The Simpsons by dressing them up for shock-value. That's what South Park does when it's not doing the same using news headlines or some hated personal enemy (at the time) as inspiration. The formula usually makes for some amusing no-holds barred comedy because often the harsh satire is warranted, but mostly it's a schtick that wears thin and it's difficult to watch an entire episode without being distracted by numerous incongruencies. And this is what is frustrating about South Park, because you know they are trying to be clever and insightful, but they are just not intelligent enough to quite pull it off and thus defer to vulgarity for a knee-jerk reaction, be it positive or negative.