I have never seen, in any class-based game, someone call someone a troll because they played as a certain class. And I'm sorry, but disagreeing with the order to do such is not 'griefing' in the least. If every player who has ever killed me as a scout is a griefer, then basically half the gamebase needs to be banned.
I'll be the first to agree that this is a little extreme, and probably the only other person than atma ballsy enough to say that this is probably just prejudice against atma. The fact that everyone I know with dislike of atma is now defending someone (a certain someone many others who have nothing against atma mostly agree is either a troll or very much pushing the limit) who, citing Bahamut's zero tolerance policy against trolling, should have been banned, is simply proof of this.
I think it's important that everyone say what they think about this. Opinions are important in a matter such as this.