Famously? People have been making jokes about farse worse matters than rape for millenia. From war, to incurable illness, to genocide, to torture, to the plague, everything has been made into the subject of a joke.
It might be a novel concept for a prudish, politically correct section society, but it's historically true.
Nothing. It has to do with the "proved" part. Something known to be true man for millennia does not get "proved".
How could you possibly come to the conclusion that "jokes which reinforce the current power structure" are equivalent to jokes about dead babies, torture or genocide? Especially after I opened my comment explaining that yes, in fact, you can make a joke about any subject matter. It's like you didn't even read my comment at all, you just glanced a keyword signifying a binary position and then you decided to dump your preconceived opinion here.
What do you think about the assymetry of, for example, the classic "[A], [B], [C] walk into a bar" jokes, where an ethnic /racial/profession/etc group C is crudely belittled and made fun of?
In practice, such jokes are seen as acceptable if C is a major/nonthreatened group, but the exact same joke would be offensive if C is swapped to a smaller/more vulnerable faction - does that match what you feel?
The simple fact is that "jokes" which reinforce current power structure are not good jokes. As a man you don't get to decide how women should feel about scantily clad ladies in technical talk slides, just as a white person you don't get to tell black people how they should feel about affirmative action. When you make philosophical proclamations about the world from a position of power you're no different from a jock making fun of a nerd because "he looks funny".
Just a modicum of empathy is all that people want in the vast majority of cases.