When my then dd5 read junie b jones I just told her that it was okay to read someone else saying the words but it was not okay for her to say them. Her kindergarten teacher told me she was reading them so much over and over that she was starting to take on junie's personality. Lol!
I personally like them to know the words so they are not over sensitive to others who use them. I just like them to know that it is not classy to use those words and I tell my kids that if other parents hear them say bad words they may not let their children play with us. They know I am serious because I don't let my kids play with kids with bad mouthes. Anyway, I think that if you teach him well, he shouldn't say the word. Dd5/6 also read and re-read diary of a wimpy kid and I was sooo not okay with that. I quickly learned she won't enact it.