Bit of a contentious issue between me and my DS' father. I really can't get my undies in a bundle about DS hearing an expletive or three in a film he's watching: he hears plenty in the street as it is. He is 9 and we have had more than one chat about 'bad words' - I have told him that using them in front of other people is bad manners and sounds particularly unpleasant when children do it, so he is not to do it, but also that it's not the world's biggest deal.
His father says that if he is watching a film clip and someone says a bad word, he has to turn it off immediately. (His father doesn't live with us, though sees him regularly). I have currently said that when he's with his dad, he does what dad says, but when he's with me, he can watch the things - though if I catch him using expletives, he won't be allowed to watch them any more.
I just think it's idiotic to prohibit a child from watching/reading something that is otherwise enjoyable or even valuable because ooh dear, waa waa, someone Says The F Word. And I am generally engaged in making sure DS grows up as free of mundane fuckwittery as possible anyway.