Yes and no. The boundary is whether or not it is comedy.
I do think that when you have established a context - South Park, a roast, etc. - where anything is clearly a joke, is provocative for comedic purpose, then I agree there shouldn't be any boundaries. Go ahead and talk about molesting children of your least favorite ethnicity.
But there is also slander, attacks on groups of people and such hate speech that is excused with a "that was just a joke". Yeah, I didn't REALLY mean *insert suitable group* are criminals, terrorists and pedos. On that there needs to be limits.