A good angle I read (but can't cite, unfortunately) is that some comedians punch up until the only people left to punch are the ones paying their salary, so the

A good angle I read (but can't cite, unfortunately) is that some comedians punch up until the only people left to punch are the ones paying their salary, so they punch down at whoever it's still socially acceptable to make fun of. And then they keep doing it until it's no longer acceptable and start making their critics the whole focus of their routine. We used to call comedians who attacked critics hacks. Now they get Netflix specials.