Without commenting on whether this presentation matches the original metaethics sequence (with which I disagree), this summary argument seems both unsupported and unfalsifiable.

1. No evidence is given for the central claim, that humans can and are converging towards a true morality we would all agree about if only we understood more true facts.
2. We're told that people in the past disagreed with us about some moral questions, but we know more and so we changed our minds and we are right while they were wrong. But no direct evidence is given for us being more right. The only way to judge who's right in a disagreement seems to be "the one who knows more relevant facts is more right" or "the one who more honestly and deeply considered the question". This does not appear to be an objectively measurable criterion (to say the least).
3. The claim that ancients, like Roman soldiers, thought slavery was morally fine because they didn't understand how much slaves suffer is frankly preposterous. Roman soldiers (and poor Roman citizens in general) were often enslaved, and some of them were later freed (or escaped from foreign captivity). Many Romans were freedmen or their descendants - some estimate that by the late Empire, almost all Roman citizens had at least some slave ancestors. And yet somehow these people, who both knew what slavery was like and were often in personal danger of it, did not think it immoral, while white Americans in no danger of enslavement campaigned for abolition.

What they did was clearly wrong... but, at the same time, they did not know it, and that has relevance.

Consider; you are given a device with a single button. You push the button and a hamburger appears. This is repeatable; every time you push the button, a hamburger appears. To the best of your knowledge, this is the only effect of pushing the button. Pushing the button therefore does not make you an immoral person; pushing the button several times to produce enough hamburgers to feed the hungry would, in fact, be the action of a moral person.

The above paragraph holds even if the device also causes lightning to strike a different person in China every time you press the button. (Although, in this case, creating the device was presumably an immoral act).

So, back to the babyeaters; some of their actions were immoral, but they themselves were not immoral, due to their ignorance.

That's the basic, some say the only, mystery of MWI: why the world operates according to subjective probability?
You'll find this question posed in the Sequence in some places.

I see morality as fundamentally a way of dealing with conflicts between values/goals, so I cant answer questions posed in terms of "our values", because I don't know whether that means a set of identical values, a set of non-identical but non conflicting values, or a set of conflicting values. One of the implications of that view is that some values/goals are automatically morally irrelevant , since they can be satisfied without potential conflict. Another implication is that my view approximates to "morality is society's rules", but without the dismissive implication..if a society as gone through a process of formulating rules that are effective at reducing conflict, then there is a non-vacuous sense in which that society's morality is its rules. Also AI and alien morality are perfectly feasible, and possibly even necessary.

Why do you think that Newtons proposal of his method of science had something to do with desire for a secular ruler?

Q: Quantum. Bayesianism isn't the LessWrong official preferred interpretation of QM because....?

Asking on StackExchange gives a variety of people before Newton: http://hsm.stackexchange.com/questions/5275/was-isacc-newton-the-first-person-to-articulate-the-scientific-method-in-europe/5277#5277

thereby creating a clearer distinction between religious and secular.

Given that Newton was a person who cared about the religious that would be a bad example. He spent a lot of time with biblical chronology.

You claimed that science wouldn't have been invented at the time without Newton. It's historically no accident that Leibniz discovered calculus independently from Newton. The interest in numerical reasoning was already there.

To get back to the claim, following the scientific method and explicitly writing it down are two different activities. It takes time to move from the implicit to the explicit.

So, this criticism is implying that simply understanding human speech will (at a minimum) let the AI understand moral philosophy, which is not trivial.

I don't disagree with the other stuff you said. But I interpreted the criticism as "an AI told to 'do what humans want, not what they mean'" will have approximately the same effect as if you told a perfectly rational human being to do the same. So in the same way that I can instruct people with some success to "do what I mean", the same will work for AI too. It's just also true that this isn't a solution to FAI any more than it is with humans -- because morality is inconsistent, human beings are inherently unfriendly, etc...

The main point is that if you buy the philosophic commitments of Descartes the hypothetico-deductive method is a straightforward conclusion. Newton might have expressed the method more clearly but various people moved in that directions once Descartes successfully argued against the old way.