https://www.lesswrong.com/posts/K9JSM7d7bLJguMxEp/the-moral-void
"If you believe that there is any kind of stone tablet in the fabric of the universe, in the nature of reality, in the structure of logic—anywhere you care to put it—then what if you get a chance to read that stone tablet, and it turns out to say "Pain Is Good"? What then?
Maybe you should hope that morality isn't written into the structure of the universe. What if the structure of the universe says to do something horrible?
And if an external objective morality does say that the universe should occupy some horrifying state... let's not even ask what you're going to do about that. No, instead I ask: What would you have wished for the external objective morality to be instead? What's the best news you could have gotten, reading that stone tablet?
Go ahead. Indulge your fantasy. Would you want the stone tablet to say people should die of old age, or that people should live as long as they wanted? If you could write the stone tablet yourself, what would it say?
Maybe you should just do that?
I mean... if an external objective morality tells you to kill people, why should you even listen?"
How is this logical? Eliezer here is calling for you to abandon reasoning or objective truths, and instead make up truths so that they are pleasant to your mind, not what is actually the truth.
Truth has no obligation to be pleasant. Something can be true and unpleasant. Ignoring truth, because it is unpleasant, is as irrational and ignorant as believing in god.
If the Universe has an "objective should", and it says that pain is good, it would be rational and logical to inflict pain.
We know why we inherently don't want pain. It is because of evolution. There is nothing divine about it. But putting your evolutionary instinct above actual truth, is irrational and ignorant.
If I remember right, it was in the context of there not being any universally compelling arguments. A paperclip maximizer would just ignore the tablet. It doesn't care what the "right" thing is. Humans also probably don't care about the cosmic tablet either. That sort of thing isn't what "morality" is references. The argue is more of a trick to get people recognize that than a formal argument.