You cannot play this trick because p-ought is grounded in what the pebblesorters actually do, which is in turn grounded in the state of the universe they aim for, which is the same universe that we live in. The humans and the pebblesorters seem to be disagreeing about something as they fight each other

Does a human being disagree with natural selection? About what, exactly? How would we argue natural selection into agreement with us?

Standard game theory talks about interactions between agents with different goals. It does not presume that all agents must theoretically be arguable into exactly equal utility functions. These interactions are not called "disagreements", they are called "games" or "problems".

You have changed the meaning of the entire ethical vocabulary in this same way, to represent a specific constant answer rather than a variable

Lemme get this straight: I'm talking about rightness as a constant, you're talking about rightness as a variable, and you accuse me of being an moral relativist?

the way you are using the ethical vocabulary it is in fact impossible to be a relativist: all ethical theories T describe some objective predicate, T-right, and any act is either T-right or it isn't. In your new language, it isn't possible to talk of "rightness" detached from any particular predicate.

You're correct that I think moral relativism is an incoherent position for the same reason that factual relativism is an incoherent position. If anything that anyone wanted were right, this itself would be an ethical theory and not a relative one. Just as if anything that anyone believed were true, this itself would be reality.

But I think that in your new use of language, you will need a word for the idea of a justification for an ethical theory, for example Kant's arguments "from first principles" in favor of the categorical imperative.

All attempts to justify an ethical theory take place against a background of what-constitutes-justification. You, for example, seem to think that calling something "universally instrumental" constitutes a justification for it being a terminal value, whereas for me this is a nonstarter. For every mind that thinks that terminal value Y follows from moral argument X, there will be an equal and opposite mind who thinks that terminal value not-Y follows from moral argument X. I do indeed have a word for theories that deny this: I call them "attempts to persuade an ideal philosopher of perfect emptiness".

My theory is unabashedly justified; it is justified by arguments on the level of morality-as-morality. It so happens that human beings are the sort of creatures that respond to such arguments, and Pebblesorters are not; but we are not trying to "be human" in responding to such arguments - the justification for doing so, is that they are right (not xyblz).

In your new use of the ethical vocabulary, this is a vacuous applause light. Of course the humans are better than the pebblesorters: you defined "good" as "the predicate that describes the particular set of things that humans do".

No, "good" is defined as that which leads to sentient beings living, to people being happy, to individuals having the freedom to control their own lives, to minds exploring new territory instead of falling into infinite loops, to the universe having a richness and complexity to it that goes beyond pebble heaps, etc.

It so happens that humans are the sort of beings who do good, and that Pebblesorters are not; but this is a mere happenstance of a moral miracle, not the justification for having fun instead of sorting pebbles.