ADVICE: Dealing with really creepy posters who've "found" you're board

okay, there's this really creepy guy who just showed up on the board that i moderate (I L B a s e b a l l) and I've had a couple run-ins with him in the past and he's using a login name of a mutual acquaintance who does not appreciate it. i noticed on ILM he's using the other guy's login name to draw attention to himself (saying troll-y things, being annoying).

i think he's kinda harmless but on the other hand, he's pulled some really creepy things on some other music related boards before. And he has shown annoyance levels of no bounds. I've got his IP (apparently he works for the same company as A l e x i n N Y C) but it's not static and seems to drift around as it's shared with many other of his coworkers.

so.... what would you do? i don't really want to welcome him on that board but i know if i attempted banning him he would react very immaturely and get out of hand leaving a big mess to mop up everyday and attempting to make the board as unhospitable as possible (as he's done before).