Unfortunatly, you cannot control your son. There are rules that you need to set up around your house though. While punishing him for this action is not in my recommendation, the fact that his disrespected you knowing that you would not be ok with him doing it in your house that you bust your butt to maintain is worth consequence in my eyes. I'm only 19 here, I'm not a parent nor am I in a place to begin a family right now. I am not telling you how to be a parents, and I AM saying that it is OK to freak out over somthing like that. I can only image what it would be like to walk in on my child.. becuase it doesn't matter how old they are, they are still your child and that is how you are going to see them... even when they are 30 years old. Let him know that you are not in support of his sexual behaviors, and while he very well might blow this off, be clear this is not about getting him to do what you want him to do/or not do for that matter. This is about creating a respectfull enviorment in your house and making a stand for what you beleive. The next time he asks somthing of you, by all means let him know that you felt disrespected by his actions and that you have no reason to make due of his request. Just so you know, I am not Mormon or anything like that, a couple years back, I was doing much MUCH worse things than your teen is right now. I am on a straight path now, I am just giving you my personal input.
I hope this helps you.
Steve