The premise of this punishment was always representative of a father's love and desire to protect a daughter. When Diana dipped her toe, into the world of the humans, she experienced love for the first time, as a human experience it. Including the pain that comes with that. Her father (the Supreme God of her realm) sought to show her the concept of physical pain, as well. She had never experienced that and he felt that her disobedience to him, warranted it. Dallas always leaved the women he punishes, with a personal hand spanking. This is a bonding technique, that also comes from a place of genuine care. He knows that this one day, will repair the cracks in the relationship she has with her father. She would gladly do this again...over and over, to achieve that.