Are you critiquing Stewart's specific implementation here? (Also weird, since that 24 minutes isn't just him saying "go fuck yourself" over and over. Not even remotely.)The guy who says PP for the first time is funny. The guy who says PP the six millionth time is not funny.
Similarly go fuck yourself offers no nuance or surprise to be considered nothing more than derogatory profanity. Repetition also drives home the lack of humor rather than enhancing it.
That doesn't mean the target audience can't enjoy it. It just doesn't really qualify as humor.
Or the use of it in general.
Because yes, it absolutely can be humour.
And it isn't just "how often it is said". Comedians tell a joke about how the basis of comedy is repetition.
The audience finding it funny might be a clue that it is humour.
Wyatt, making proclamations about what is objectively humour is probably a bad idea.