A bully rarely finds their actions wrong. They rely on their friends and peers to justify their actions. It happens to children, and it happens to adults. As a society if we taught love and compassion as much as we do violence and hate we would grow so much.
Try to stand up to a bully at any age, and see how fast their friends rally to their defense. Watch and see how fast someone comes forward to speak up for the person being bullied.
Be that person who stands up. Stand up for yourself, and stand up for someone who is weaker than you.
Never allow yourself to fall into the role of a bully.