You need money to sue someone... a lot of money. >.<
Also I believe you have to actually know who exactly it is that you're suing. He could easily have said that it wasn't him, someone hacked into his account and he didn't know who it was... or that MentaL was just framing him.
Also, unless I'm remembering incorrectly, he got punished by MentaL's own hand somehow... I'm not sure of the details, though.