I'm probably not going to pick the correct words for this, but I think there is a difference between violence and aggression.

Think of how a pack of wolves asserts the dominance hierarchy. They are aggressive towards each other. But they do not want to actually hurt one another because that would weaken the pack.

However, they would be violent against an opposing pack.

The purpose of internal aggression is to impose order. Order is important for the proper function of a group.

Violence is usually costly, and should be avoided whenever possible. Aggression seems like it has a place in society.