Violence is used where all other methods have failed. When you can't convince someone through persuasion, when you feel desperate, when you need something badly, when you have deep hatred, then violence is the sad answer. Strong people use love, weak people don't have love, so they resort to violence. Violence is cowardice.
A child learns best through gentleness, and love. You have to be patient with children, you need to explain calmly. Every child has angelic qualities. But some of us use or abuse the power of our age and impose our force on children. We beat them up. Can you beat an angel ? A child once beaten is lost forever. You can't rule the heart with force, you can only control the body. If you wish to rule the heart, learn the art of love. Violence is cowardice.
Legal systems have been designed to protect human rights. You don't have a right to carry out your own form of justice outside the legal framework. You have no right to use violence as a form of justice. It is illegal. Violence is cowardice.