Getting angry is often a counterproductive or harmful response. For one thing it takes time and generally accomplishes nothing. Emotions are not rational and lead to actions that are not rational. This results in wife beating and child beatings and other pointless violence and harmful responses to stimuli. So feeling anger is ok only if you can control your actions when you are angry. Generally unless it stimulated you to take useful action on some issue it is pointless. Typically it is just an emotion you need to release to keep it from building up.
I just typed half of a long response to this and it was lost to the void, but here goes again.
I agree with much of what you're saying - anger can often lead to negative consequences. Sure. On the other hand it can lead us to do things that are good for us too.
It may lead a man to beat his wife, but it can also lead his wife to be unwilling to accept being beaten. She may get so angry she leaves him, fights back, calls on the aid of friends or relatives or the police, gives him an ultimatum, or some other course of action to deal with the problem (she may just nip it in the bud the first time he raises her hand to her by shouting "don't you ever ****ing hit me" and meaning it). I think that's one of the reasons we have this emotion at all - because sometimes we need it to spur us to do dangerous or difficult things that nonetheless we should do. Then again, sometimes it doesn't work out in our favour and a guy shoots his wife and her lover and ends up in prison for the rest of his life.
That's not good for anyone involved, but sometimes anger (or it's potential) can be good for everyone. The fact that you know that I would be angry if you tried to steal from me makes you think twice about doing it - you know that I might become physically violent, call the police, or again, do something else to "get back at you", and the threat of this helps to deter you from stealing from me, or in any other way taking advantage of me.
Now, don't get me wrong, I'm a pretty laid back guy. Usually if something makes me angry I think about it for a while, decide it's nothing, and an hour later I've completely forgotten about it. But sometimes it doesn't work out that way.
The problem is that I used to be a little too laid back for my own good. I assumed that other people wouldn't want to take advantage of me, because I would never want to harm them, and I based my view of others on my view of myself. Well, then I got a glimpse of the real world. After actually being taken advantage of a few times (though never horribly) I realised that it was better to protect myself. I started getting angry when it seemed like someone was going to take advantage of me.
For example, shortly after moving to china my employer sorted out my visa. When we were negotiating before I came here we made some agreements, amoung them I said that I expected them to get me a work visa.
Well, when it came time to do the paperwork they expected me to pay for:
- The hospital bill to get the health check necessary for a visa. (around 1000rmb)
- The visa application and processing fees. (don't remember but something similar I think)
This made me very angry. Because of that anger I refused to pay. This may sound eminently reasonable, but understand that I had very little money, had been unemployed for four months, and didn't have anywhere else to go. Then again, they didn't know that.
When I demonstrated my anger by first talking calmly, but later rather agitatedly, loudly and forcefully, particularly when pointing out that they were not being true to their word, they relented and got the documents sorted out and payed for. I am glad I got angry in that case.
There have been a few more clashes between me and them and in every case anger is the only reason that I fight back. I'm glad that I do as I can tell that they are testing me to see how far I can be pushed, and if I give an inch, they'll take it. (For instance, one of my colleagues wasn't carefully checking if she was being payed for all of her working hours, then one day she found out that she was being underpaid every month.)
The most recent example is when they said that I would have to double my working hours without being payed any more, and that this was in accordance with Chinese labour laws. We went back and forth between them saying "according to your contract and the laws of the country we can do this" (and on and on for about 10 minutes of that) and me interrupting them yelling "I don't care. I won't do it. I have plenty of other options. If you don't back down I'll just leave."
After a while they suggested that this new policy would only apply to the Chinese staff. After much more yelling on my part (and some more subdued arguing one the part of one of the Chinese girls) they said they'd think about it, and we never heard about it again.
On all of those occasions I'm quite glad that I got angry. I think that both I and some of my colleagues are better off because of it. So I don't think that anger is always a bad thing - but I agree that was should try to be rational about it. If you think about something that made you angry and find that it's just ego, or something meaningless, often it is better to just let it pass, but sometimes the opposite will turn out to be the case.
It seems disrespectful to me! 
