Morality and sin were originally designed for the group. They were not designed for the whims of the individual. The individual can create a subjective version of morality, that applies to themself. While the needs of the group requires an objective version of morality, that has to apply to all. This is more difficult to do, but the ancients were smart enough.
This is similar to the laws of nature and science. We do not form a law of science, based on a single scientist, making a single observation of a singular thing. Many scientists would test, many things, under many situations, to make sure the law is universal, and not an isolated pet theory.
For example, thou shall not steal. A thief can come up with rationalizations for why they think stealing is good for them. The evil rich deserve it. That guy is a miser. He yelled at me and I am getting even. But if we asked a million people if stealing was good; universal application, the rules will be different. More good can be done, for more people, if we do not steal, if everyone works, and if neighbors help each other; charity. This is a universal law, like gravity. The ancient took the hard road toward universal application.
In terms of the universal laws of gravity, an individual may image a world were there is no gravity, so they can move around freely, never get saggy skin and even fly. This fantasy world may be satisfying, for one, but it may not appeal to all. A more universal law for gravity, would leaves the private fantasy worlds behind, and accepts reality as it is. It would also learn how to manage within a physical reality, that we all share and that we all can verify. Science defined a universal law for all. This may not appeal to the fantasy minded but it does the most food for all, since it is real.
The Atheists are not that rational, since they tend to assume an individual style fantasy morality. They assume this is better than an objective reality for the entire group. This why they always have to tell us just how rational they are based on science affiliation; distraction.
The original approach to morality became the model for defining universal science theory; has to apply to all the data and not just your favorite data. Although some modern science theory has become dissociated; many theories for some things, due to the influence of the atheist fantasy morality. Math can be used to simulate game physics engines; fantasy, as well as reality physics. Math and subjective physics assumptions allows infinite lives in games. This appeal to the fantasy world of gaming the system for personal gain; Laws of man.