Groupthink.
Edit: Per discussion below, I should clarify that I'm referring to a particular think that a particular group engages in("political correctness"), not the psychological phenomenon in general.
Ah, I see what you mean. Thanks for explaining.
And, sure, if nobody can seriously express the sentiment that women nag more than men do, or that men are more irresponsible than women, then being able to humorously express the sentiment that all women nag and all men are irresponsible is, as you say, a useful way of averting groupthink. It's not good, but it's better than nothing.
I'm not nearly as confident as you sound that the premise is true, but I agree that the conclusion follows from it.
As Multiheaded added, "Personal is Political" stuff like gender relations, etc also may belong here.