The "f-word" was in a movie script, not Will's mind. It's not like he walked up to the director and said "Hey, can we change this word 'crap' to 'f***' just to make the movie more entertaining?" It's not like he;s never said a cuss word in his life. And when he does, he uses it with meaning, not just abusing the word. So it really isn't a big deal. I'm sure all of us have sworn at least once in our lives.