Yes, but were these demons not of the burning legion? I don't think Illidan would have attacked Azeroth while trying to attack Argus. That would have been the stupidest move he could have made, so either he was stupid or Illidan and the Azerothians were betrayed and we need to apologize to Illidan. So he doesn't need that redemption arc.
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Yes Illidan was fighting the legion, the greatest enemy known to the universe (at that point in time). So why did we take him out? Seems kinda like we shoot ourselves in the foot there...