Stop being polite. don't "shush" him. Turn around and yell at the top of your voice, "would you two guys shut the hell up?, I can't hear the director!!!"
You can't be the arbiter of behavior unfortunately. There will always be dumbasses in High School. The director I'm sure sees it or at least how crappy he performs in marching, If it's a class, then he'll get a bad grade.
you need to speak to the director, whether he want to deal with stupid crap or not. That's his job.
You also should just try to ignore him. Trying to act like a goody two-shoes and getting mad at him because he doesn't follow the rules is a no-win situation. If he is saying things about explicit sex, tell the director that he is saying inappropriate things about sex and that you are uncomfortable with it. They will have to deal with as a sexual harassment situation and remove him or suspend him. (of course it will probably get your *** kicked) But try to get moved to another area in your section away from him. Other than that you can't do anything. If the director doesn't care then you shouldn't either.
As long as his poor marching doesn't cost you a competition, just forget it. Life's to short to be worrying about idiots who don't do what they are supposed to.
It the parent's fault for not spanking kids anymore. Kids need to have their butts spanked when they misbehave. Today's youth are uncontrolled sociopaths who face no consequences for misbehaving.
Why should he care? Nothing's going to happen to him.....right?