Trash talk from my 6-year-old

Well, it has happened. This afternoon while discussing the plan to wear flip-flops the entire time in the Y locker room with my 6-year-old (in order to avoid contracting Staph), he blurts out the phrase "piece of s#*t." Now for that brief moment in time I had stepped away from him to retrieve his jacket from the closet, so there was a possibility that I had not heard him correctly (crossing fingers). Instinctually, I replied, "What did you just say?" "The floor's a piece of shit." Me: "Where did you hear that word, who says that?" "John*," he respectfully replied, "it means something's a piece of trash or dirty." At least he used the word in the proper context. Trying to muster all of my control and calling on all of my best parenting skills, I attempted to not let him get too much of a reaction out of me. "There are some words in the English language that are offensive, which means they bother people. That is one of those words. If you mean that something is dirty or is like trash, then please say 'dirty' or 'trash'." Of course during my mini-lecture he tried on the word a few more times, and even spelled it out. When I had finished talking, he replied, "Well, John says it." "Yeah, well, I'm not John's Mom, and he's very lucky I'm not because if I were I would be washing his mouth out with soap." So, there you have it. It has happened: my children are forcing me to sound like my mother.
*Names have been changed to protect the not-so-innocent.