Spanking demonstrates that it's all right for people to hit people, and especially for big people to hit little people, and stronger people to hit weaker people. Children learn that when you have a problem you solve it with a good swat. A child whose behavior is controlled by spanking is likely to carry on this mode of interaction into other relationships with siblings and peers, and eventually a spouse and offspring.
But, you say, "I don't spank my child that often or that hard. Most of the time I show him lots of love and gentleness. An occasional swat on the bottom won't bother him." This rationalization holds true for some children, but other children remember spanking messages more than nurturing ones. You may have a hug-hit ratio of 100:1 in your home, but you run the risk of your child remembering and being influenced more by the one hit than the 100 hugs, especially if that hit was delivered in anger or unjustly, which happens all too often.
Physical punishment shows that it's all right to vent your anger or right a wrong by hitting other people. This is why the parent's attitude during the spanking leaves as great an impression as the swat itself. How to control one's angry impulses (swat control) is one of the things you are trying to teach your children. Spanking sabotages this teaching. Spanking guidelines usually give the warning to never spank in anger. If this guideline were to be faithfully observed 99 percent of spanking wouldn't occur, because once the parent has calmed down he or she can come up with a more appropriate method of correction.
be a good role model