[barrkel]

I think it's more subtle - and more simple - than that. When someone uses an inoffensive professional tone, they sound fake.

Like the way a salesperson or a teacher is fake, when you meet them in those roles, rather than in a social setting of equals.

This barrier of "professionalism" is exactly what the careful use of profanity is trying to puncture. It's not the only way to puncture it; and not everyone is comfortable with puncturing it, or having it punctured. But it may be worth it for the people who prefer the closer connection.

Professionalism, almost by definition, implies distance. Your emphasis on it actually convinces me that profanity is even more useful in presentations than I thought it was; I very seldom use profanity except in the company of people I know very well, but having had this exchange with you (combined with TFA) I may use it when I next give a talk.