You need to have a serious conversation with him about the language situation and let him know in no uncertain terms that he needs to watch his mouth. While boys may hear that kind of language at home, in school, on television, etc. - scouting is meant to be a place that is a cut above the norm where the behavior expectation is set at a higher level. If you deal with this seriously and with the tact and concern you demonstrate on this forum, he will understand and tone it down.
I have a similar adult - likes to think he is 'one of the boys'. Tries to be fun-loving and a pal. One day, he thought it would be cute to 'moon' some campers. I drew some boundaries for him and things have been fine for the past several years. In these situations, its almost like dealing with a pre-adolescent boy. We need to remind them sometimes that they are now adults.
Good luck.