You're wrong. Enforcing someone to refrain is exactly what he's talking about. You are asking someone to do something if you are asking them to refrain from speaking, as it's their liberty to speak.
You're misinformed if you think children above 1st graders have never heard the "f bomb." Also, what's the problem with them hearing a word? Can you explain how hearing an expressive curse word ruins your child's innocence? I mean, seriously, you sound like the type of parent that would never let their kid watch SpongeBob until their 16.