I charged into his room, and I said firmly that he should pack his bags and leave.

Finallyyyyyyy. Honestly, sorry dude. My brother is a total jackass and gave my parents hell for 8 years before they finally kicked him out for good. Just a bit of advice - don't let him back in. Yes, he is your son, but people don't change over night or over the course of a few weeks. Especially if the only thing that has happened to them has been that they're now living with an equally fucked up person.

My parents fell for this 3 or 4 times. They'd kick my brother out, 6 months later he'd come back pretending he'd changed. In reality the friend he was staying with, who was just like him, had kicked him out.

Your son won't change. Dude is fucking lost.

Not to be an armchair psychologist either, but i think your family got off easy - cornering girls much younger than them, stealing their underwear and listening to them while they're with their boyfriends? Thats some creepy shit and you MUST know that that isn't as far as it could've gone.