I hope others are learning about Diablo through word of mouth instead of finding out the hard way (like you did).
Sorry this happened to you, wish I had a scroll to replace it for you...unfortunately, I don't.
It seems a lot of people have already been suckered into thinking he is a reformed player. If players want to deal with it in game, merely don't interact with him. If he shows up, leave. Sure he (along with his buddies) may try to kill you but it can become a very boring game if nobody will deal with you.
-Val'lyn