This is true regardless of whether the "things you can't say" are true.
Not quite. The joke is more likely to resonate with the audience if it corresponds to their experience.
Nevertheless, I agree that the joke is no substitute for an argument. It's necessary to get society to the point where it's possible to make the argument without being declared unfit for polite company.
The joke is more likely to resonate with the audience if it corresponds to their experience.
Or their biases, or their culturally-acquired beliefs...
As Multiheaded added, "Personal is Political" stuff like gender relations, etc also may belong here.