Yeah, South Park's a good example because Cartman often is a villain- he's anti-semitic, narcissitic, sexist and very violent at times.
For me, Cartman doesn't reflect badly on the creators because he's not the sort of character that the audience is expected to identify with, plus (in terms of the anti-semitism) there's the counterbalance of Kyle to give a different viewpoint, and there's a lot of complexity with the characters, so you see racism as fitting in the context of his spoilt and aggressive personality.
On the other hand, I do find Family Guy to be often quite racist, as there are a lot of 2 dimensional characters (like Mort the Jew), who seem to exist purely to make stereotypical jokes about, without the complexity or counterbalance of South Park, and the occasional nod of knowingness doesn't quite do enough to persuade me otherwise.
But, yeah, everyone has a different opinion. I think, whenever you produce anything creative- you'll rise in some people's estimation and go down in others'.