Crazies like this want attention because they're sad and have nothing better to do with their life. If you and your friends starve him of attention, he'll get mad at first and struggle really hard to get it then eventually give up. I don't have personal experience, but I've read a decent amount of crazy interweb stalker stories.
When he's desperate for attention you might get something to ban him with, otherwise again I suggest completely ignoring him.
