There was a weirdly high amount of people basically telling him he deserved it and should accept the consequences of his actions and not get his artifact as a result, as if killing the Cenarion Circle NPCs was a genuinely bad thing he needed to be punished for.
It's cool if your actions have consequences, but I feel like applying the concept to getting barred out of the 6th xpac content for being hostile to a vanilla faction is taking it too far.
Personally I'm hated with Booty Bay on my druid so I can't turn in any quests I get from Island Expeditions there.. not sure if I'm ever gonna do anything about it though