The drive to emphasize a person’s “masculinity” by engaging in rude or offensive behavior is interesting. Some of the most confident and masculine men I’ve ever known were absolutely not trash-talkers; they were kind, considerate, well-spoken people who knew when to be considerate, and also knew when to get aggressive with bullies.
For whatever it’s worth, teach your son to keep the “yo mama” jokes to himself when around African-Americans. I attended a junior high school in L.A. where a majority of the students were bused in from downtown, so we had a student population that was majority African-American. Whenever a kid dared to say the words, “yo mama,” it was a sure bet that he was about to have his ass kicked from here to Mississippi. It was serious business and, oftentimes, multiple other kids would join in the beatings as other students would link arms and form concentric rings around the fights so that the administrators and teachers couldn’t intervene.
I guess what I’m trying to say is that your son might think he’s pretty smart, but if he utters the wrong words in front of the wrong people, it could easily get ugly.
The other kid was fully justified in telling his parents about your kid’s behavior. There are a whole lot of people in the world who would not be okay with these comments, even if they were made “in jest.”
It’s good that you’re concerned about it, and I know that you want to do the right by your kid. As someone already mentioned above, we no longer live in a society where the wife-beating asshole wins. Teach your son to socialize with all kinds of kids: older kids, younger kids, black, white, brown, rich, poor, smart, not-so-smart, etc., and teach him to make friends with girls, too! There is nothing worse than a grown man who’s never learned how to socialize with women (and vice-versa). It is a HUGE handicap in life.