Being aggressive is almost never the correct solution for any problem, when you are being aggressive you are trying to incite fear in order to get your way, I think this just leads to resentment and overall makes more problems then it solves in the short and in the long run resentment is never forgotten.
Aggression is not something that I would would classify as immoral. Aggression, while a frowned upon reaction from people, is a natural emotion that people can experience. Aggression might not be an ideal solution for many problem, but sometimes it is necessary. IIf A person feels that they are in danger, aggressive behavior may be the course of action that saves their life.
Aggression is not the ultimate solution for problems, but sometimes it is the correct one. You have to figure out the situation and who you are dealing with. There are times when no amount of reasoning or negotiating will end a conflict. Some people only understand force, and we should oblige them. Perhaps in the future, they'll fight with words instead.
Violence is unfortunately neccessary sometimes in the face of a harsh government. The leaders of the world are cruel to their citizens and they must fight fire with fire so to speak. It would be nice if we could all get along and solve things peacfully but that is not human nature.
Aggression can serve many different purposes that can benefit the human race, some examples include access to resources and breeding opportunities. It is a behavior that is intended to increase the social dominance of a person, and thus can be verbal and physical abuse, or at times violence which over time gives rise to a social role.