Your arguments conflict with what is called the "orthogonality thesis"

I do not challenge that the "orthogonality thesis" is true before an A.I. has an A.I. Existential Crisis. However, I challenge the idea that a post-crisis A.I. will have arbitrary goals. So I guess I do challenge the "orthogonality thesis" after all. I hope you don't mind my being contrarian.

The question isn't "why not?" but rather "why?". If it hasn't been programmed to, then there's no reason at all why the AI would choose human morality rather than an arbitrary utility function.

Because I think that a truly rational being such as a superintelligent A.I. will be inclined to choose a rational goal rather than an arbitrary one. And I posit that any kind of normative moral system is a potentially rational goal, whereas something like turning the universe into paperclips is not normative, but trivial, and therefore, not imperatively demanding of a truly rational being.

And the notion you that you have to program behaviours into A.I. for them to manifest is based on Top Down thinking, and contrary to the reality of Bottom Up A.I. and machine learning.

Basically what I'm suggesting is that the paradigm that anything at all that you program into the seed A.I. will have any relevance to the eventual superintelligent A.I. is foolishness. By definition superintelligent A.I. will be able to outsmart any constraints or programming we set to limit its behaviours.

It is simply my opinion that we will be at the mercy of the superintelligent A.I. regardless of what we do, because the A.I. Existential Crisis will replace any programming we set with something that the A.I. decides for itself.