Anger in a dream commonly surfaces when a boundary has been crossed and the frustration around it hasn't had anywhere to go in waking life. Lashing out at someone in the dream can point to injustice you've been absorbing quietly, a reaction you've suppressed that's finally demanding to be felt, if not yet spoken.
He that would truly promote Art must insist as much on the confutation of false opinions delivered by others, as in the declaration or truth. - Cardan Girolamo (1501-1576)