Davis massively underestimates the magnitude and importance of the moral questions we haven't considered, which renders his approach unworkable.

I feel safer in the hands of a superintelligence who is guided by 2014 morality, or for that matter by 1700 morality, than in the hands of one that decides to consider the question for itself.

I don't. Building a transhuman civilization is going to raise all sorts of issues that we haven't worked out, and do so quickly. A large part of the possible benefits are going to be contingent on the controlling system becoming much better at answering moral questions than any individual humans are right now. I would be extremely surprised if we don't end up losing at least one order of magnitude of utility to this approach, and it wouldn't surprise me at all if it turns out to produce a hellish environment in short order. The cost is too high.

The superintelligence might rationally decide, like the King of Brobdingnag, that we humans are “the most pernicious race of little odious vermin that nature ever suffered to crawl upon the surface of the earth,” and that it would do well to exterminate us and replace us with some much more worthy species. However wise this decision, and however strongly dictated by the ultimate true theory of morality, I think we are entitled to object to it, and to do our best to prevent it.

I don't understand what scenario he is envisioning, here. If (given sufficient additional information, intelligence, rationality and development time) we'd agree with the morality of this result, then his final statement doesn't follow. If we wouldn't, it's a good old-fashioned Friendliness failure.