Outrage is believing things are one way while seeing that they are another. That's why expressions of outrage are usually followed by, "I can't believe that...".
Parents get outraged by their children's behavior, citizens get outraged by government corruption...in fact anyone with any amount of belief in something or someone is likely to feel outraged when confronted with information that doesn't fit the belief. For example, after years of developing my intellectual defenses by reading Chomsky, David C. Korten, Adbusters, etc., I comprehend how the corporate media is structured. I understand what it is designed to do. So when I see clear bias in the news, I am no longer outraged by it at all. That doesn't mean I still don't think it wrong or wish it were different, just that I'm not outraged.
But when a person finally sees things for how they actually are, the outrage dissipates. I know the US government is a corrupt sham, so any additional information I get which exposes this further doesn't really make me feel anything. If I know that a family member is a lazy bum...it doesn't really outrage me when he leaves yet another job on the first day.
So maybe when we feel outrage, in the interest of truth and clarity we should think about and attempt to change the beliefs we hold which may be inconsistent with reality.