Angry because of something that is wrong or not fair. (Cambridge Dictionary)
In a manner indicating anger or annoyance at something perceived as unfair. (Oxford Dictionaries)
Feeling or showing anger because of something unjust or unworthy : filled with or marked by indignation. (Merriam – Webster)
If you are indignant, you are shocked and angry, because you think that something is unjust or unfair. (Collins Dictionary)
Stock Photo – A young girl loudly screams and indignantly gesturing with her hand.