Moral Equality?

The particular version of the foregoing question I address in the following pages is this: What nontheistic reason or reasons do we have, if any, to accept the morality of human rights, a core constituent of which is the right to moral equality: the right of every human being to be treated as the moral equal of every other human being in this sense: as equally entitled with every other human being to be treated—as no less worthy than any other human being of being treated—in what Article 1 of the Universal Declaration of Human Rights calls “a spirit of brotherhood.” By “the morality of human rights” (as I call it), I mean the particular morality embodied in the Universal Declaration.