Discuss behavior after playdates.
Disrespectful behavior or a blatant disregard for rules requires a conversation with the friend’s parent—but not generally annoying actions. Since parents are protective of their kids, use gentle language and a non-confrontational tone when you bring it up. Say, "I noticed when the kids were playing the other day that Billy used some language that I don't allow in my home. It made me uncomfortable and I'd rather it didn't happen again."