It is just that in today's modern PC-protective world, even vintage Sesame is dogged for being too risque when it was eventually accepted for its time period.
Which is a big reason why I don't think PC is the way to go.
You're right,
South Park does not need to use foul language (though again, it's not for children). And definitely, not everyone has to like it. However personally, I think they do it in a humorous and well placed manner and not just "for the heck of it." They even did an episode that said people shouldn't curse every other word.
And sadly, there are TV shows that don't use any curse words, but then have no message at all (or at least not helpful ones). I'm just saying cursing is not the biggest problem we have.
And ultimately, people young and old should know better than to shape their behavior and personality solely off a TV show. It needs to begin in the home. And while I think TV should provide a good example, it should not be expected to raise children.
"Let us...recognize that we are bound together
In our desire to see the world become
A place in which our children
Can grow free and strong."
(That's a song called "Shed a Little Light" by James Taylor. It was written for Martin Luther King, but sung for Richard Hunt at his memorial.)