The Course statement that anger is never justified† is often interpreted as a criticism rather than a fact, leading to the idea that anger is wrong. Nothing could be further from the truth! Anger is not good or bad; it’s simply the result of believing blame thoughts. It is this fact to which the Course points.
Blame thoughts originate from the idea that something other than the self is responsible for a situation the self doesn’t like. Such thoughts are founded on the idea that there could be a separate self, and a world that acts upon that separate self. In Truth there is no separate self, and there is no world; separation is an idea of the mind.
Accepting that such thoughts are present is the means by which responsibility for those thoughts is accepted‡. Be careful though; don’t make the mistake of assuming that taking responsibility means taking responsibility for thinking such thoughts. Such thoughts are reflexive, the result of learning and conditioning. You are not your thoughts. Thoughts appear in the mind—which you are not—and not in Spirit—which you are. Taking responsibility for such thoughts simply means acknowledging that belief has been given to separation thoughts appearing in the mind.
When blame thoughts appear in the mind, rather than reacting from those thoughts, what if the decision is made to stay open to seeing things differently? It may be difficult at times—anger is a potent feeling in the body, and can cloud the ability to think and act clearly. Letting anger subside—whether it be through physical activity that helps release the energy of it, or through some other activity that helps ground and center the mind—is a helpful step toward opening oneself to seeing things differently. Being open to seeing things differently allows a deeper understanding to dawn, an understanding which can bring action that is justified, and which resolves conflict and heals separation rather than perpetuates it.
†”Anger is never justified. Attack has no foundation. It is here escape from fear begins, and will be made complete.” (T-30.VI.1)
‡”Anger always involves projection of separation, which must ultimately be accepted as one’s own responsibility, rather than being blamed on others.” (T-6.in.1:2)
Understanding A Course In Miracles 
“All anger is nothing more than an attempt to make someone feel guilty…” (T-15.VII.10)
I’ve been pondering this one for a while now. Your post, that ‘anger is never justified’ is another one that I’ve found not easy to understand at first, though it surely speaks to sanity in the world rather than its opposite, which would be insanity endlessly repeating itself. If our original ‘sin’ was to feel guilty for our perceived voluntary separation from God, then, well, that’s a whole lot of guilt! If we have all this guilt inside of us then getting angry in order to project that guilt onto another in order to get rid of it seems to follow logically. Of course, this can never work if we are all the Sons of God and are all one with God.
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