The golden rule may originate from Christianity, which it doesn't, by the way. The golden rule, or the sentiment of the golden rule, exists way earlier than Christianity. If that's true, right, even if it was true that it originated in Christianity, the foundation for moral truths or ethical values or to be a valuable person, the sumum bonum, would not become the rule itself. It would remain God. God would be the source and foundation and summit for these moral rules, even if the rules were universal.