my opinion.
anger arises due to violations of psychological attachments. anger serves its purpose in the context that it arises.
my explanation of violations of psychological attachments:
i have my sphere, this is my reality, it contains me, the self. the self is everything that the self attachs to itself psychologically. my beliefs, my values, my rules, principles, etc. oh and my body, which is attached to me too. (by a very fine silver chord)
my sphere, this reality also contains "not me", the world and other people, not self. some of the not self is attached and some is disattached (or detached even, who knows), my parter is attached, my family, (not all of them) my home, the earth itself.
some of the not self is disattached. people and things i dont like or care for, and those evil entities that violate my sphere of psychological attachement.
the self lays claim to all these elements in its sphere: "This is my House(welcome)" "my car, (touch it not)" "My City (be careful) " "my beliefs, (fear the lord your god)" etc
a violation occurs when one of my attached components is damaged or threatend. somebody throws litter in my garden, outrage. talks to my girlfriend in any kind of way other than "just being nice", my values or beliefs being frowned upon or even, god forbid, disputed.
of course, i dont get angry myself, being the enlightend being that i am, without psychological attachments and no egotic ideas.

a way of supplanting courage
are we talking anger or agression and are we differentiating between the two? if just anger please elaborate.