Pope Francis Says Christians Do Not Exist Outside The Roman Catholic Church. Recently the Pope made this statement because in 325AD the church unified all the sects and standardized the religion officially called Christianity which gave them every right to make that claim since it is their sect and their doctrines.
The Golden Rule on the other hand owes its creation to no one nor can anyone manipulate its rules, doctrines, or by-laws. The Golden Rule does not have a membership you can join nor does it take sprinkling or dunking of water to make anything official but rather the Golden Rule does require all of us to die to ourselves putting aside our own desires by putting others first which gives everyone the only available benefit for doing the Golden Rule, having others treat you like you have treated them. This is, of course, is what gives us the power to determine what kind of life we will have here while attending our earthly finishing school.
By calling yourself a Golden Ruler or starting an organization called the Golden Rule will not allow anyone to enjoy the benefits of the Golden Rule since the only way to have it work is to just do it. So while religions require adhering to their many doctrines or holy events the Golden Rule simply requires us to live it and then enjoy the benefits, not of membership, but of living it.