This is rather general and therefore has to be seen in specific cases.
Some people believe in ideal and their passion for it become almost religious, and this category can be genuinely outraged at something that they do not believe is right.
On the other hand, it can be superficial – a guilt trip, thus makes oneself feels better in condemning something one or his group are guilty of. This is probably more common and could be the reason for the political correctness.
Genuine outraged should be resulted from real belief. In other word, it has to be religious or nearly so.