"The ultimate weakness of violence is that it is a descending spiral begetting the very thing it seeks to destroy, instead of diminishing evil, it multiplies it. Through violence you may murder the liar, but you cannot murder the lie, nor establish the truth. Through violence you may murder the hater, but you do not murder hate. In fact, violence merely increases hate. Returning violence for violence multiplies violence, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that." Martin Luther King Jr.
World War II and the US civil war didn't ended the violence, it just changed the way that violence manifests. If you look in many groups on Facebook, 9gag or redit , you will see Violence in protests are being used to create more hate in people who hates. I really believe that the society was improved by ideas not wars.