You seem to be making the tacit assumption that no one really values morality, and just plays along (in egalitarian societies) because they have to.

Let me clarify. My assumption is that "Western liberal meta-morality" is not the morality most people actually believe in, it's the code of rules used to keep the peace between people who are expected to disagree on moral matters.

For instance, many people believe, for religious reasons or pure Squick or otherwise, that you shouldn't eat insects, and shouldn't have multiple sexual partners. These restrictions are explicitly not encoded in law, because they're matters of expected moral disagreement.

I expect people to really behave according to their own morality, and I also expect that people are trainable, via culture, to adhere to liberal meta-morality as a way of maintaining moral diversity in a real society, since previous experiments in societies run entirely according to a unitary moral code (for instance, societies governed by religious law) have been very low-utility compared to liberal societies.

In short, humans play along with the liberal-democratic social contract because, for us, doing so has far more benefits than drawbacks, from all but the most fundamentalist standpoints. When the established social contract begins to result in low-utility life-states (for example, during an interminable economic depression in which the elite of society shows that it considers the masses morally deficient for having less wealth), the social contract itself frays and people start reverting to their underlying but more conflicting moral codes (ie: people turn to various radical movements offering to enact a unitary moral code over all of society).

Note that all of this also relies upon the fact that human beings have a biased preference towards productive cooperation when compared with hypothetical rational utility-maximizing agents.

None of this, unfortunately, applies to AIs, because AIs won't have the same underlying moral codes or the same game-theoretic equilibrium policies or the human bias towards cooperation or the same levels of power and influence as human beings.

When dealing with AI, it's much safer to program in some kind of meta-moral or meta-ethical code directly at the core, thus ensuring that the AI wants to, at the very least, abide by the rules of human society, and at best, give humans everything we want (up to and including AI Pals Who Are Fun To Be With, thank you Sirius Cybernetics Corporation).

Can't that be done by Oracle AIs?

I haven't heard the term. Might I guess that it means an AI in a "glass box", such that it can see the real world but not actually affect anything outside its box?

Yes, a friendly Oracle AI could spit out blueprints or plans for things that are helpful to humans. However, you're still dealing with the Friendliness problem there, or possibly with something like NP-completeness. Two cases:

• We humans have some method for verifying that anything spit out by the potentially unfriendly Oracle AI is actually safe to use. The laws of computation work out such that we can easily check the safety of its output, but it took such huge amounts of intelligence or computation power to create the output that we humans couldn't have done it on our own and needed an AI to help. A good example would be having an Oracle AI spit out scientific papers for publication: many scientists can replicate a result they wouldn't have come up with on their own, and verify the safety of doing a given experiment.

• We don't have any way of verifying the safety of following the Oracle's advice, and are thus trusting it. Friendliness is then once again the primary concern.

For real-life-right-now, it does look like the first case is relatively common. Non-AGI machine learning algorithms have been used before to generate human-checkable scientific findings.