Aggressors can easily have you emotionally on the run. But you gain power when you hold ground. The best way to do that is to keep emotion out of things and judge and deal with behavior only.
Confrontation, done well, ensures that the spotlight falls where its light needs to shine the most: directly on a behavior of concern.
Assertive behavior is a key element of healthy, independent, adult functioning. But because asserting oneself is a form of “fighting” for one’s legitimate needs, it’s easy to get confused about the difference between aggressive and assertive behavior.