Explain why it is relatively more difficult than building a Clippy,, or mathematically solving and coding in morality.

I think we've hit on a serious misunderstanding here. Clippy is relatively easy to make; you or I could probably come up with reasonable specifications for what qualifies as a paperclip, and it wouldn't be too hard to program maximization of paperclips as an AI's goal.

Mathematically solving human morality, on the other hand, is mind bogglingly difficult. The reason MIRI is trying to work out how to program Friendliness is not because it's easy, it's because a strong AI which isn't programmed to be Friendly is extremely dangerous.

Again, you're trying to wrap "humanlike plus epistemically and instrumentally rational" into "rational," but by bundling in humanlike morality, you've essentially wrapped up the Friendliness problem into designing a "rational" AI, and treated this as if it's a solution. Essentially, what you're proposing is really, absurdly difficult, and you're acting like it ought to be easy, and this is exactly the danger that Eliezer spent so much time trying to caution against; approaching this specific extremely difficult task, where failure is likely to result in catastrophe, as if it were easy and one would succeed by default.

As an aside, if you value rationality as a goal in itself, would you want to be highly epistemically and instrumentally rational, but held at the mercy of a nigh-omnipotent tormentor who ensures that you fail at every task you set yourself to, are held in disdain by all your peers, and are only able to live at a subsistence level? Most of the extent to which people ordinarily treat rationality as a goal is instrumental, and the motivations of beings who felt otherwise would probably seem rather absurd to us.