Anger is simply our insecure ego's self defensive mechanism.
Actually, all anger comes from thwarted expectations. Only one of those typical expectations held my most people is that they will not be attacked. It is reasonable to expect that when someone exits a previous agreement, they will so inform you, that you may change your expectations. Do what you choose without harming others by violating their free-will choice. For every dichotomy there is a transcendent position which accepts the whole dichotomy.