Real or perceived does it make a difference? You see a man slapping a woman in the street. She is crying. Do you intervene or walk on by? In exactly such a circumstance my dad intervened and got a mouthful - from the woman. Was my dad not normal? Was he suffering an attack of moral outrage? Should he have ignored it? Probably. It was none of his business, was it?
It's a great example - and I've been there, albeit with a different result.
It's a real event, happening in real time. If it's experienced, it's visceral and very real - a 'moral outrage' has been witnessed first hand - psychologists argue that primal instinctive urges come to the fore. It's based on your world view, it's a reaction to the 'moral compass' being impinged upon right in front you.
When 'moral outrage' is perceived, you are considering how you feel out of context. The fight or flight mechanism is diluted, or not triggered, so it's a rational process, again based on your world view / conditioning. The same biological mechanisms are not in play.
feel sorry for your dad now - see, vicarious empathy........