Freightdawg has it right. "Appropriate" means "approriate to the venue" and there may be places where obscene slogans on T shirts are not considered offensive, but not all venues are the same.

I'm all for making the audience think, challenging conventional views etc., but the T shirt slogans mentioned don't express any constructive thought or say anthing original. I've seen plenty of far wittier ones that do.

Anahata