Unfortunately linguists believe the "F" word will be common vernacular in the American dialect by 2025 or so. So pretty much beyond some pretty harsh treatments (staples, tongue removal, etc.), you pretty much have to except that you are fighting for an older more dignified time for language. If it is your child; I suggest reprimands in public, and strong (significant) punishment in a more private setting. With adults, you can only make the request and speak your opinion.
