Victims aren’t always virtuous. That’s a sad lesson that people learn from life. Human beings have a benign instinct to help those who are hurt through no cause of their own. But those they help don’t always turn out to be very grateful.

And sometimes it’s hard to be sure just who the victim is. The most heavily publicized and violence-prompting police killings of young black men — in Ferguson, Mo., in 2014, and Milwaukee this month — appeared to be, as the facts became known, justifiable responses to felons’ assaults.