All moral/ethical debate is of this form, at least for a broad-enough definition of "rights". Since moral debate does seem to exist in the real-world, the argument that it cannot would seem to be quite wrong. And in fact moral debate might even be strategically useful, if only as a way of searching for shared Schelling points (i.e. focal/coordination points) that can be more easily defended even in a stricter 'political' sense.