And now there is research to prove it.
How do you teach a child that hitting is not okay by spanking if he or she hits another person?
A recent study found that when children were spanked, their tendency toward aggression increased by 50%. In addition, they found that although spanking may stop a child from misbehaving in the short term, it becomes less effective with repeated use and "it makes discipline more difficult as the child gets older and outgrows spanking."
I believe that parents teach values through their words and deeds. That's why we have never spanked our children, and it's also why we do not allow violent videogames. How can we teach children that violence is not the way to solve problems, when they are allowed to play shoot 'em up games and simulate violence?