Oh.
So, OK, if you don't think it's true that the use of stereotypes in humor is a safety valve to avert groupthink, I'm not exactly sure why you said that when I asked, but I'm happy to drop that line of discussion.
Now you seem to be saying that the use of stereotypes in humor is a safety valve to avert censorship... do you actually think that?
It's a way of saying things that aren't supposed to be said. Whether the level of "supposed to" is a bit of moral outrage(like it is today), or a gulag(like it was in the Soviet Union), people use jokes to get around barriers. That serves the function of evading censorship sometimes, as well as the function of undermining certain kinds of groupthink to a certain extent. It's not perfect, but it serves a role.
As Multiheaded added, "Personal is Political" stuff like gender relations, etc also may belong here.