I've had this debate with my mates
Piracy is obviously wrong, but you wouldn't arrest the mayor of a town with a high crime rate would you. He has created a virtual city and provided the means to commit crime, but there's no proof he's taken part.
On the flip side you would arrest the man who sells a gun to someone who says I'm want to buy a gun to rob a bank, and then goes on to rob a bank... So it's swings and roundabouts.
On the subject of Piracy, at some point (if not reached already) there will be more people illegally downloading media than those that purchase it legally. But the law of the land is the law of the people... so you can't have most people doing something illegal?... Does that make sense? I've confused myself.