Throughout history, rules have changed. In Victorian England it was OK to chain a mentally ill person to a pilaster for passersby to taunt and abuse as they would an unprotected animal in a zoo. The rules changed and then it was criminal to treat people this way.
The rules changed, but the morality stayed the same. It is cruel to treat less fortunate people like berated animals to be laughed at and scorned. Happily, at this stage of our planet’s history, if someone did that to another human, they would be prosecuted.
When we depend strictly on rules for our morality, we are going along with the fashion of the times. And when these rules are heavily enforced, it implies that they do not come naturally to us and so we must be frightened into obeying them.
True morality does not come from some external source that threatens punishment. It comes from our own inner reflection on how it would feel to us if we behaved in a certain manner or someone behaved in that way towards us. I do not harass the less fortunate because it doesn’t feel good in my heart to do so—not because someone is watching to see if I break the rules. That is the lasting source of true morality and not someone holding a big stick over my head.