When I see an injustice, I get angry. That kind of anger can be energizing, and move me to act before the opportunity is lost. That way, blunderers learn to step more carefully.
This happened to me recently. I was working late when the cleaning lady came by. She told me how wonderful I must be to work late so many nights (yeah, right). She was ingratiating to the point of annoyance, but I gave her the benefit of the doubt. Until she picked up my photo album and saw a wedding picture of my daughter and son-in-law. She pointed at him. "Those People", she said, "Back in my country, they cause a lot of trouble. There is too many of them, back in my country." I saw red. With, I think, commendable restraint, I turned my back and refused to talk to her any more. Maybe a little passive, but I figured it was good enough for the moment.