The short version:
He broke and / or bent every single rule barring the hacking one, when he finally was confronted by the admins for this he decided to bitch, whine, argue and insult the admins. I believe his banning wasn't for one offence, but more a whole stack that eventually broke the admincamel's back including, not exclusive to: flaming, spawncamping, blocking OC's with structures, voice spam, hogging the command chair and lying to the admins.
To be honest, the guy was a wanker.
Also, ignore most of the thread that Jefe posted, the only thing worth reading is Uranub's reply which is goddamn hillarious, pretty much everything Saltz says is bull^^.