it's hilarious because it's meant to mock reality. That's what comedy is. Mocking reality.
Once you start putting up limitations, you ruin the entire purpose of the genre.
For example:
Imagine going to a play, all actors are professionally trained in drama, the play is meant to be a tragedy, but no facial expressions and no tonal changes to reflect mood are allowed.
or
You're watching Nascar, but all drivers have to put their car in neutral and push it around the track because they can't use gas.
or my favorite example:
"YOU HAVE FREE SPEECH*"
* - you can't say this, this, this, this, this, or this. aka you don't actually have free speech.
At some point, comedy is going to offend someone at some level. If you watch South Park, you know for a fact that they don't put restrictions (or prefer not to put restrictions). They make fun of everyone and everything.