To be fair...if you follow the links to the original CNN article, Bristol did a little cussing of her own.
“She said she jumped into a fight after “some old lady” pushed her sister, Willow Palin, because “oh f***in’ hell no, no one’s gonna touch my sister.””
http://www.cnn.com/2014/10/21/politics/palin-brawl-audio/
Interesting that the audio with that article does not include the quote you posted, only the reporter’s quote of what she said. I would have thought they would include that bit of audio, being more damaging to Bristol because she isn’t quoting some foul-mouthed pervert.
All that to say...my bs detector is on high alert.