Oh, no I'm not saying you're angry, I was using "you" in the general abstract sense. I'm sorry if that came off as personal.
But I think anger can help you. In the moment, sometimes - anger can help you get that money back, if you chase them down and get it back. Sometimes it doesn't. Most of the time it doesn't. But I'll tell you what never works. Not getting angry, no matter what people do to you. Everyone loves someone like that. Someone they can treat as a doormat because they won't even get angry on their own behalf. If someone's constant mockery didn't make you angry, you'd never come to face them about it and tell them to back off. You would never establish your boundaries, your rights.
But I'm talking about something bigger than that, too. Beyond just the moment that made you mad.
If you're angry about a friend who got kicked out of home and lives on the streets, maybe you can't help that friend. But that anger may motivate you to do something about the problem, to help others in need. Some people use their righteous anger to set up institutions and try to stop the same thing from happening to other people. Anger can motivate justice being served in the courts too - you wouldn't appeal a case if the outcome didn't make you angry. Without anger, we can't feel we have the right to do what's just - I could go as far as to say it's the crucial emotional basis for justice. (In case anyone says it, yes, justice is subjective, but many morals are still agreed on by most of us and it's better to have /some/ form of justice than total anarchy, right? Because /that's/ when anger would really get out of hand.) Without anger, rights simply can't exist because we have no emotional drive to enforce them.
Misplaced anger can do a lot of harm, yes. But the fact is, we /can't/ stop it from happening by not being angry ourselves. If we suppress our own anger, righteous or not, people who let their anger drive them to do terrible things will only get away with those things more. If there is no one angry at what they are doing, they are /allowed/ to do it again. And the only way to prevent ourselves from acting on misplaced anger is to understand the basis for that anger. We're only human, and we will be angry, so we should use it productively by acting on the anger we feel is justified, and working out anger that isn't. By acting on anger, I don't mean punching someone in the face, I mean speaking to that person, or appealing for change. Unless they stole your money - then by all means, tackle them and take it back if you feel you're up to it - but don't hurt them beyond what's necessary.
So yeah, anger may not always work for that particular event that made you angry, but in the long term I'm saying it's a change-creating fuel. As long as it doesn't get out of hand.