Being AFK isn't against the TOS and shouldn't be considered an exploit. All your arguments are invalid.
That being said, the TOS also says AeriaGames can ban for any reason; any reason including 'no reason'. So they can ban you because they want to, because a GM has personally deemed it cheating.
I see how this can upset a lot of people, but power is going to be abused, when simply not being gifted would send the message just fine. power corrupts everyone, even in lowly positions like GM, get used to it.