There are “plenty of examples” of bad acts arguably being justified by the result. Whether they were “necessary” is generally only arguable. And I wager engaging in violence to defeat “dangerous people” more likely made things worse most of the time. There are the times when not engaging in violence was tremendously effective, most notably as led by Gandhi and by MLK Jr, which weighs heavily against the idea that violence is “necessary.”
Sometimes violence is necessary, like in self defense. Also WWII, Hitler had to be stopped. Mrebo, don’t you have gun for self defense and defense for your home?