I am not saying that the language should be there or that it somehow makes a film or even a song any better, but if the artist made it that way, that is their choice. If I don't like what is said in a song or a movie, then I don't have to continue watching/listening and that is my choice. If it is bad for my kids, then my KIDS don't need to watch it...until they are old enough.
You can't entirely shield kids from the real world and that is a fact, because if you think that they haven't heard that language and worse on the playground then you are dreaming. That doesn't mean you let them swear like a sailor. Violence, sex and language all carry a similar weight to me as well in films. They have their place in film and again, if you are offended, then don't watch it and don't let your kids watch it. Even a film that deals with adult themes - death, factual accounts of tragedy, infidelity, etc... are all things that kids don't need to be exposed to either, but nobody is complaining about those.
What really needs to happen, IMHO, is that the kids just need to be taught the difference between a movie and reality. On the same note, I don't want a watered down version of anything, because life doesn't come that way.