I don't see the social hierarchy as a form of oppression. And I don't see how this says anything about political correctness, either.
I'm not at the top of the ladder. I'm not particularly funny, and I'm not particularly cool. But social domination, on the part of anyone, doesn't really feel like oppression, to me.
While they didn't outright mention oppression or political correctness, those terms often go hand in hand with a term like "aggression".
The author also mentions: "But both sexes use comedy as a means of controlling others".
The authors also imply that men do it to be mean because they make jokes about others, but women are wholly innocent because they only make jokes about themselves.
"Aggression" and "Controlling Others" have negative connotations and to equate them with humor in general is unfortunate. The authors of this study need to lighten up.
Being politically correct is like trying to pick up the clean end of a turd.