“Dad, what does ’pervasive’ mean?” My daughter asked me the other day. 
“It means something that’s all over. Like a bad smell.”
“So pervasive language is bad language?”
What had caught her 11-year old eye was a movie poster for The Taking of Pelham 123. She said the movie was rated R for “pervasive language.” I was reasonably certain she was mistaken. Perhaps the poster said “pervasive foul language?” No, she insisted. It just said “pervasive language.” I forgot about the exchange until I found myself standing on a subway platform yesterday evening. The Child was right: 
Pervasive language? You mean there’s talking in every scene? Well, thank goodness for the warning! I want my summer blockbusters full of chase scenes and explosions, thanks. If I want dialogue, I’ll just stay home and watch Masterpiece Theatre.
A quick Internet search shows the MPAA has been using “pervasive language” to justify “R” ratings for at least 15 years. A 1994 movie titled Once Were Warriors earned an R for “pervasive language and strong depiction of domestic abuse, including sexual violence and substance abuse.” Still, just about every movie since Al Jolson’s The Jazz Singer has featured pervasive language. Perhaps it’s an appropriate warning for David Mamet or Woody Allen movies, but it’s hard to justify as a synonym for “offensive” or “foul throughout.”
A common teaching strategy is to have kids use context clues to puzzle out the meaning of unfamiliar words. It helps if those words are used correctly.
I think the problem isn’t so much the misuse of “pervasive” its the misuse of “language” to mean “foul language.” Movies are rated PG-13 simply for “language.”
Wow. No matter how hard I ponder the word, I can’t figure out how “pervasive” could mean what the MPAA seems to think it means. Could it be a 15-year-old malapropism? It’s hard to imagine what similar word they’re confusing it with.
Perverse, perhaps?
No, once you redefine “language” to mean “foul language” it all makes sense. PG-13 can have isolated instances of “language” but if the use of “language” becomes pervasive then the rating has to be R.
http://www.mpaa.org/flmrat_ratings.asp
And once you redefine “dirt” to mean “dollars” I’m a rich man.
Interestingly, Rachel, the MPAA page you helpfully referred to says “an R-rated motion picture may include adult themes, adult activity, hard language, intense or persistent violence, sexually-oriented nudity, drug abuse or other elements, so that parents are counseled to take this rating very seriously.”
Hard language is more descriptive, and has fewer characters than pervasive. I wonder how the convention (if it is indeed a convention) to use pervasive took precedence over the MPAA’s own descriptor.
But I think they mean pervasive hard language, analogously to persistent violence. PG-13 movies can have *isolated* incidents of the same words and/or actions — so its not necessarily different words/action that get you to the different rating but how persistent/pervasive they are in the movie. My reading is that pervasive means what it usually means (extensive, thoroughly penetrating) but that “language” is the euphemism.
However, the misreading of “pervasive” to mean “perverse” may have encourage the shorthand.