This American Life's 6/11/2004 episode, "Propriety", includes a half-hour segment on foul language and the absence of scientific evidence that it hurts kids, despite that assertion being the basis of FCC policy. The abstract:
Act One. Government Says the Darnedest Things. The FCC says it just wants a little civility on the nation's airwaves. And by tightening the rules on what swear words are allowed, government officials say they're protecting kids. The only weakness in their argument is that the facts don't happen to back them up. Ira talks with Dr Timothy Jay, author of Cursing in America and Why We Curse, and John Cody, legal aide to FCC Chairman Michael Powell.
High points of Jay's research: kids all know the words and use them the same way grownups do; no one, kids or not, thinks of graphic sexuality when they hear the F-word used merely for emphasis; there is no evidence that people swear any more today than at any other time in the history of the English language.
And yet everyone interviewed, including the kids, agreed that bad words are embarrassing and impolite in many contexts. Ira Glass's editorial comment at the end is that perhaps propriety rather than alleged harm to children should be the basis for a more balanced policy on foul language on the airwaves.
It would have been nice to have heard some cross-cultural data. There's a perception among anglos that certain terms carry a lot less weight in African-American usage than in the American English spoken by whites; I wonder whether that's a myth of the same kind as a belief that language has deteriorated in recent generations. And yet I know from geographical variations in Spanish that sexual terminology for emphasis is much more common and much less emphatic in Mexico than in many other places. (There's a funny illustration of that in the movie El Norte, when a couple of Guatemalan hitchhikers know they've crossed Mexico's southern border upon meeting their first Mexican truck driver. :-) )
To hear the clip you'll need to go to the This American Life 2004 archive and scroll down to episode 267.