I realize that typing this is probably a waste of time and energy, but there's nothing "right wing" about South Park at all. You're seeing patterns of "bias" when there aren't any.
I've said before that even if South Park is right wing 51% of the time and left wing 49% of the time that still puts it WAAAAAAAAY more right wing than Family Guy or most shows on TV.
The thing is, South Park is neither right wing nor left wing. It's not a politics show.
It's very political, but in a much more subtle way. Take the shadow endorsement of Ron Paul in the "Faith Hilling" episode. To quote the co-creators of the show, "we hate conservatives, but we
really hate liberals." I agree with Night Man that they take on everyone though.