We don't say F*** because in our language it is an insult so we dont say it because we respect the people we are talking to. The world would still be flat if everyone was as narrow minded as you.
Yeah, but who taught you 'f***' was an insult? In German, the word 'Fotze' is extremely offensive, but I'm sure it means nothing to you (assuming you're not German

), because nobody ever taught you not to say it. That doesn't mean it's not offensive - if you ever said that in the presense of a German he'd kick your ass.
The point is, now that I told you that 'Fotze' is incredibly offensive, will the sound of the word now conjure the same feelings as if I said 'f***'? If someone called you a Fotze, would you react the same way as if someone called you a 'f****r'?
I'm thinking not, because the word 'Fotze' and its connotations are not inherent in your psyche.