Research evidence shows that children who have been slapped or hit are usually so overwhelmed with anger and hurt feelings that they cannot remember what they were punished for. There is all the difference in the world between using your strength to snatch a child away from a hot stove or prevent them running into a busy road, and intentionally causing pain as punishment. Yet it does. That's because hitting doesn't work except to relieve parents' feelings. We are not saying that hitting at home is the only cause of that violence, but we are saying that ending hitting at home would help to reduce it.
Children model a lot of their behaviour on their parents.
Parents who use physical punishment are directly teaching their children that physical force is an acceptable way to get what you want. If we want less violent adults we have to bring them up believing that physical force is not acceptable. When serious cases of child abuse are investigated, they are frequently shown to have started with occasional smacks given in the name of discipline which gradually escalated into tragedies. Current acceptance of physical punishment causes a dangerous confusion. Most of those responsible for seriously injuring children are found to have been physically punished in their childhood.