In my view anger is:
…the display of frustration or annoyance of a behavior or series of behaviors.
Why is this important? Well, when I mention that “anger is understandable but not acceptable”, most people tell me that they cannot control their emotions.
Now I would simply respond by agreeing with them and state that I think that we can however, control the behaviors, our own and others, before they frustrate or annoy us.
rethink PERFECT 
I was reading my bible this morning and came across this verse and thought of some of what you have written, of course I’d also been thinking about it before today.
Col 3:8 “But now you must also rid yourselves of all such things as these: anger, rage, malice, slander, and filthy language from your lips.”
Anger indeed is unacceptable…it’s not something to accept, but understand. I have come to understand that anger should be a flare, nothing more, a sign that you should put your emotions in check. So when I feel anger rising, I ask myself, what do I do next, I cannot allow it to grow, and then I start to laugh, which helps to quell what’s happening inside.
Yeah I agree Toni. How about this:
anger is an indication of how much we have planned or prepared for the future.
I think that the more we learn to understand anger and its triggers, the less it is likely to happen.
I think there is a co-relation between anger and the lack of understand of it.
But it still does not explain how some people justify their anger as “righteous indignation”?