So then why must one live by the code of another, can they not live for the sake of living? If one loves themselve's enough, then they must certainly love all. To say that one cannot love without certain add ons, is to say that none can love at all. To preach the word of another is too be part of a fold, no originality, no true concept of self, a machination of a system.
I could say it's the herd mentality. If we, as humans, were theoretically able to separate ourselves from everyone else from birth, learning to think for ourselves, and then eventually came upon another human or many, we would flock to those who were like minded, the same way other animals do.
Why not just accept others as they are? There should be no reason, no reward, just good company, personal opinion be damned. Love for the sake of loving, never expecting, giving of the self, wanting only a friend. Though the point of view be different, we are still the same. Expecting that a friend be of like mind, is having only the self for a friend.