Really, this should be obvious to everyone. People get angry because their mind, consciously or subconsciously, detects that anger will be beneficial to them. Period. If you are oppressed, but are very weak, and know you are weak, and you know that anger won't make things better, then you do not get angry. You grovel or you submit. Whereas anger can happen in all sorts of circumstances where there is no true grievance or oppression, ranging from a child throwing a tantrum because he wants candy, to an aristocrat getting angry at a peasant for bumping into him.
Well, I think the mind's detection that anger would be beneficial operates at lower-level, and that in a modern environment it can misfire. For instance, let us say that an employer screws you over. Your primal instinct might be to get angry and make a big fuss. This is because in a more traditional environment, where everybody knows everybody, you need to get angry and fight for yourself, or else you will be seen as a pushover. Your primal instinct also recognizes there is no immediate danger to getting angry at your employer -- you can yell at them and raise a consequence without him beating you to a pulp. So your instinct says: "Get angry, defend your honor, it is in your interest to make a fuss."
But in a modern environment, few people, if anybody, know that you were screwed over by your employer. So there is no need to put up a fight in order to defend your reputation. Furthermore, if you put up a fight, onlookers will not be close enough to the issue to know if you are right or wrong. All they will see is drama, and they will associate that drama with you, rightly or wrongly. You will make an enemy of your former employer. So all around, anger is a bad idea. So in the modern environment, Dale Carnegie advice applies. Also good advice for the modern world is Chris Matthew's adage: "Don't get mad, don't get even, get ahead."
I also think that most modern bosses act in a sort of weak-willed fashion. Remember the classic scene from Office Space where the boss asks Peter to come in on Saturday? As typical for the modern boss, he says, "What's happening? So I'm going to need you to come in tomorrow, if you could be here around 9pm, that would be great." Rather than phrase it as an order, he makes it sound like he is asking for favor. Thus the boss doesn't pattern match your primal mind as being a boss. You have to reprogram your mind to understand that what he says is really an order, and not a favor. You have to reprogram your mind to treat your boss like a boss, and not like a peer you can get angry at.
This explains what you see when haggling with a merchant in a street market. They're not angry or indignant; they are well practiced in a critical skill.
"People get angry because their mind, consciously or subconsciously, detects that anger will be beneficial to them" sounds like armchair science. Do you have anything to back up this claim?
Psychology is not a science in the same way that Newtonian physics is a science. The best way to understand human psychology is to have lots of life experience, to share experiences over beers with others, and to read good books that have the experiences of other people, past and present. My claim about the nature of anger fits the observations that I have made myself and observations that I have heard about second hand. In my posts here http://devinhelton.com/2015/03/23/standing-up-to-offense-bul... and here https://devinhelton.com/2015/04/02/offense-bullying-ii-the-b... I present lots of examples from the real world that are in line with my theory. If your life experiences are counter to my theory, that would be interesting new evidence to hear about.
For example, one observation I have seen dozens of times, is that teenagers get much more angry with their parents for slights that are far more minor than slights suffered at the hands of friends and peers. Why? Teenagers know they can get angry at their parents, and suffer no consequence. If they unleashed the same obnoxious outrage upon friends, they would soon be friendless. The different responses are not conscious – knowledge of the power relationship is internalized, and the anger arises from subconscious calculations.
If you want something scientific though, the Selfish Gene by Richard Dawkins has some excellent sections about how tendencies in animals to fight or to retreat, or in animal children to cry for food or to be silent, are best explained by the game theory of what will have the highest probability of passing on genes.
"There is perhaps no phenomenon which contains so much destructive feeling as 'moral indignation,' which permits envy or hate to be acted out under the guise of virtue." – Erich Fromm
I guess we can now rewrite 'virtue' to be 'reason'.
Really, this should be obvious to everyone. People get angry because their mind, consciously or subconsciously, detects that anger will be beneficial to them. Period. If you are oppressed, but are very weak, and know you are weak, and you know that anger won't make things better, then you do not get angry. You grovel or you submit. Whereas anger can happen in all sorts of circumstances where there is no true grievance or oppression, ranging from a child throwing a tantrum because he wants candy, to an aristocrat getting angry at a peasant for bumping into him.