The problem is that teaching people to restrain their impulses using a fear of punishment is totally different from getting them to change their behavior becaus

The problem is that teaching people to restrain their impulses using a fear of punishment is totally different from getting them to change their behavior because they understand why the behavior is bad. When you simply punish someone without teaching them to understand you create a system of unwritten rules where the person is unsure whether any particular action will result in a punishment or not. But if you can create an understanding of why the action was bad then you can give the person a toolset to understand whether their future actions will be bad. And hopefully you can create a society of people whose behavior is determined by their understanding of right and wrong and not by whether or not they think they will be punished for something. I think you're grossly oversimplifying the way people work if you don't see the difference here.