James 1:19, 20 – My dear brothers and sisters, take note of this: Everyone should be quick to listen, slow to speak and slow to become angry, because human anger does not produce the righteousness that God desires.
The anger that this verse is talking about does not produce righteousness into our lives.  Instead, it divides us from others and allows sin to infect our relationships and ourselves.  Anger can destroy marriages, friendships, and even prevent opportunities for promotion at work, or any endeavor in our lives.  When we are quick to listen and slow to anger, we are bridging a gap of communication that may be disconnected or misappropriated with the person we may be in conflict with.
As fighters, if you are in a situation where you are fighting for the defenseless, do not become angry.  It will only distort your view, and can cause harm for you and those you want to protect.