The prefrontal cortex, which is one of the best developed areas in human beings, is really important to representational thinking or the ability to manipulate ideas and thoughts. Those functions of the brain aren't completely mature until early adulthood. Well, that circuitry is overlaid and connected to the circuitry of emotions. So the two work hand in hand. Aggression, the ability to use force, is a natural part of the behavior repertoire of living things.
Aggression is important.
If we couldn't be aggressive, we couldn't defend ourselves, or our children. We wouldn't be able to compete for jobs or compete in sports. But when that normal behavior becomes inappropriate, when it is directed toward the wrong person, in the wrong place, at the wrong time, and with the wrong intensity, then it becomes violent and it becomes unacceptable. When that happens, there is a change in the person's ability to accurately determine whether something is a real threat. Either they are overreacting to benign stimuli, or they are not reacting to very real threats, like the threat of punishment.