What if I like to treat myself terrible and hurt myself everyday? It's okay for me to treat others that way?
Just because something has a long history (secular or otherwise) doesn't give it any merit by itself.
If we need some standard to judge against what is morally acceptable in the case I presented (no this doesn't apply if you like to hurt yourself and others) then you are back to defining a standard which cannot inherently be neutral.
1. I believe GP was suggesting "golden rule" as the basis for governmental-wide rules to be enacted, not that each person should use unique rules based on their own "do unto me" preferences. (If actually applied, "What if this were done to me" also helps to get around the issue of people enacting rules only on other groups, as they wouldn't actually want to be personally treated the way they're proposing.)
2. Regardless, if basing rules on whether someone would want those rules to apply to them does not have merit, is there some better basis you'd recommend?