South Park is not a show to watch if you don't have skin of iron.
They go out of their way to offend as many people as possible, but I think they do so in a way that's indiscriminate. They even try to offend themselves.
It bothers me less depending on how old the episode is, and the overall tone of the joke. Older “let’s put this guy in a dress for cheap laughs” type stuff is lame, but not as bad as more recent attempts to make hatred more palatable by disguising it with a thin veneer of “humor”.