Parrots use their beaks for many more reasons than aggressive biting.
Most people consider any biting to be aggression.
By our own reactions to a bird using its beak, we can actually cause the bird to begin a lifetime of biting. It is a mistake to measure bird behavior by human ideas of right and wrong. Fear is easily sensed by any bird. If you display nervousness or fear, most parrots will react negatively. Parrots are not birds of prey, but in fact are the prey.