It would be better not to get too serious over this and burden them with all sorts of lectures. This is adolescent behavior and should be recognized as such. Be sure to watch your boys' behavior. If you start to see hostility toward others, that's when you need to be concerned.
Boys can be a handful.
This is an important problem to nip in the bud, because it so easily carried into the schools and our society. A good friend who teaches at a Christian school recently mentioned that foul and crude language had become a problem in her first grade class. Bad language has become so common that many parents are becoming apathetic. Parents who choose to spend quantity time with their children have the benefit of providing immediate correction when the offending words pop out of their children's mouths. Although children may experiment with bad language just to test others' reactions, parents may need to restrict or replace TV shows, books, or even friends or activities of their children.