A lot of standup recently in Australia is around our multiculturalism - minorities laughing at themselves, and wonderfully at the rest of us. I think it suggests we're in the midst of redefining our identity.
"The dozens", specific to my culture ("your mother's so fat...") came about as traditionally a way to work off aggression without violence (which would've been punished by mainstream society). It was directed internally and not at that society. It's one of the reasons I find the practice rather offensive. I know where it comes from.
How highly we value self-deprecation.
truth in jest.
If it's about first impressions, we ought to eschew the vulgar and profane.