If we are merely the ones who make our own rules, we make rules that are consistent with the behavior that we produce. So when we make the rules, we fudge and we make the rules to include as morally appropriate the behavior we most like to do. We do that all the time. That's why I think this sense of offense that we feel inside is so significant and why it was profound when he realized that this offense is not an offense that we are taking against ourselves. Our morality is too small to justify the sense of offense that we feel inside.
Someone is offended.
It's not us. It's someone outside of us and someone who is bigger than us morally. We feel morally guilty, and we feel more guilty than we ought to feel if it's only ourselves that we answer to. Our awareness of true moral guilt implies we have broken a true moral law made by a true moral Lawgiver, who stands outside the system and passes judgment. The reason we feel guilty is that something tells us that we ought to have done something else.