Yeah! I'm with 'spaw on this one!

Perhaps a letter stating the real meanings of what they're singing could do some good... Gods know it'd be better than some pusilanimous "we're sorry we're singing, we just don't know any better" apology before the song.

Maybe something along the lines of "Back in the days of sail, there was little worse on board a ship than a man who was drunk on watch. The sailors despised such a man to a point as to create a shanty specifically laying out the punishments due to such an offender."

Couldn't hurt.

M