You believe in the golden rule because it is a Christian concept. Because you live in a Christian country. You are like the fish who lives in the water, but doesn't believe in the water. You benefit from it being there, and it has molded you, but if everyone thought like you it wouldn't exist.

I do believe that you're a moral person, and I don't think you need to be a Christian to have morals. But keep in mind, morality is not a fixed concept. It can be wildly different in different countries. It is Christian countries and our morality that has created the philosophy of freedom, individual rights, charity, science, many things.