angry at a perceived injustice
indignant - angry
If you are ‘indignant’ then you are aggrieved or shocked about a situation that you feel is unjust or unfair, usually towards you or your interests. The term connotes a type of righteous anger that can be justified, or can veer into haughtiness and sanctimoniousness. It is a formal word that is most commonly encountered in written English.
The politician became indignant when questioned about her alleged role in the scandal.
Paul is filled with a sort of righteous indignation that makes him feel he has the right to criticize others for their bad behaviour, while ignoring his own.
The remark was totally unfair, but instead of responding indignantly, I kept my cool.