Am I wrong To Believe That Spanking Teaches Violence?
From Q and A in Child Discipline By James Dobson (1976)

I believe you are, but you've made an important point. It is possible for parents to create hostility and aggressiveness in their children by behaving violently themselves. If they scream and yell, lashing out emotionally and flailing the children for their accidents and mistakes, they serve as models for their children to imitate. That kind of parental violence is worlds apart from the proper disciplinary approach. However, when the child has lowered his head and clenched his fist, he is daring the parent to take him on. If the parent responds appropriately (on the backside) he has taught the child a valuable lesson that is consistent with nature's method of instruction. Consider the purpose of pain in life. Suppose two-year-old Peter is pulling on the tablecloth and with it comes a vase of roses which tips over the edge of the table, cracking him between the eyes. Peter is in great pain. From this pain he learns that it is dangerous to pull on the tablecloth. Likewise, he presses his arm against a hot stove and quickly learns that fire must be treated with respect. He pulls the doggie's tail and promptly receives a neat row of teeth marks across the back of his hand. He climbs over the side of his high chair when mom isn't looking and he learns all about gravity. For three or four years, he accumulates bumps and bruises and scratches and burns, each one teaching him about life's boundaries. Do these experiences make him a violent person? No! The pain associated with these events teaches him to avoid making those same mistakes again. God created this mechanism as the child's best vehicle for instruction. The loving parent can and should make use of the same processes in teaching him about certain kinds of social dangers. Contrary to what it might seem, Peter is more likely to be a violent person if his parent fails to apply this principle, because he learns too late about the painful consequences of acting selfishly, rebelliously, and aggressively.