I've read the reasons he provided, and have to say they're not much valid in my opinion.
First- Yamcha as a member of underdogs: I don't see if it is a crime being a member of underdogs, AND yamcha denies it (and I don't see why I shouldn't believe him). Plus, if he's really trolling, 'till he does it in Underdogs forum I don't see why he shouldn't keep weakening the adversaries
(J/k)
Second- Yamcha doesn't contribute to the forum: he is actually one of most active members.Took part to Abandonia collaborative art project, is translating Abandonia to Bulgarian, and some other things, including NOT posting disgusting images in the "What the Hell" thread.
Third- Yamcha spammer: Undeniable, yamcha used to spam some time ago. But since the warn level is on (and even some time BEFORE) he stopped, as far as I remember. tell me when did he spam last time.
This said, I think that warn should be removed.