Shit happens.
I'd say turn the tables, instead of dealing with him abandoning you, abandon him. Have everyone except a select few to remove him from their friends list. And if it works out as planned, he'll come crawling back, hopefully wiser.
Of course it could backfire, but thats all I got.
And both guys and girls do this shit all the time. I know a girl who is hooked up with this total asshole, and all he does is talk down to everyone and threatens people. He even got her to start doing drugs. (Granted me and my friends stoped that real quick). She broke up with him many times, each time swearing never to go back, yet she keeps going back.
Sometimes, people are just slaves to their emotions, which is sad.