Why can you swear more in a documentary?

I'm glad that the current trend of classification decisions (e.g.; The King's Speech) show the BBFC easing its policy on strong language at 12A. It really is a trivial matter compared to things like violence and drug abuse. (And ideally, the Americans would follow suit.)

But here's a question of consistency : why are you usually only allowed to swear once or twice in a work of fiction, whereas documentaries like 'Capitalism : A Love Story' and 'Senna' can get away with a lot more, like four or even five? Surely the concern of children copying aggressive words are exactly the same? Is there really a qualitative difference if it's Ayrton Senna telling someone to go ƒuck themselves instead of Wolverine?








"I've already let the right one in. Why would I let you in?"