One thing you must accept in comedy is that anything and everything is a legitimate target. It's nothing new, only something that we've been "spared of" by decades of political correctness.
Black can be funny, Irish can be funny, and killing Kenny can be funny; so can dueling comedians on crutches and Big Gay Al....
Can't make yourself ineligible or immune unless you are willing to write off the entire genre.
It was Carol Burnett who once said, "Comedy equals tragedy plus time"
Complaining that some humor is "inappropriate" misses the point that all humor is inappropriate. If it were appropriate and proper, it wouldn't be funny. Of course there are degrees, and Parker/Stone push the boundries. But they are the boundries of the comfort-zone, not the humor-zone.
My $0.02...