In all seriousness, if the whole guild got banned because of that, rather they were actively participating or not, is bullshit. If not, they in no way violated any terms/agreements. Even if they did I'm not too sure they violated anything. You can't call it cheating to use an item given to you in game, even if it was a GM's fuck up. Getting banned for using an in-game item getting banned for playing the game. He didn't hack the game to get the item to anyone's knowledge, so where does Blizz get off with this shit? "We screwed up so we're going to ban your entire guild."
Makes me wanna stop being a customer of theirs if their solution to their fuck ups is to ban their customers.