The first thing you can do is to try to tone down the rhetoric—in other words, to do all you can to avoid the shouting matches. I know that isn't easy, and you may be facing very tough issues with your son—but do you honestly want this to be his strongest memory of home? I hope not.
After all, arguments like this probably don't change his mind—and they don't persuade you to change yours, either. They only end up poisoning your relationship, and five or 10 years down the road you both will regret it. The Bible wisely says, "A gentle answer turns away wrath, but a harsh word stirs up anger" (Proverbs 15:1). Sometimes it's better to say, "Son, you know we don't agree with you, but we love you, and we don't want you to do something you'll only regret later on."
The most important thing you can do, however, is to pray for your son and urge him to submit his life to Jesus Christ. God loves him, and He doesn't want him to wander aimlessly through life. And if you've never committed your own lives to Christ, do so now.
Right now, your son wants his independence, and that is understandable; he is on the brink of adulthood. But when we leave God out of the picture, our desire for independence can turn into our worst enemy. The Bible warns, "The way of a fool seems right to him, but a wise man listens to advice" (Proverbs 12:15).