Three words: Dread Pirate Roberts.
As a PC, they can get away with it due to their swagger or charm, applied as needed. I'd encourage that viewpoint in the player rather than the football hooligan viewpoint that you fear.
Otherwise, why be an adventurer and do all these good things? Assuming part of their adventures includes rescuing people, defeating the bad guys etc.
Unless you're playing an evil PC campaign, in which case, no trubba anyway. Also, try that shiznitz on a desert tribe settlement or an isolated hill town inland and they'll be all, "the what pirate who?", and "Jolly Roger this (stab)!", surely.