My 5 year old uses profanity

Why would you hit your child for something the has so OBVIOUSLY learned from someone else? He is only 5 years old. Someone in the home obviously uses profanity and he learned it from them. The home is a child's most important clroom. Either he picked it up from someone in the home, from television, from friends of his parents. This sort of language has to be taught. Children aren't born knowing profanity.