Doesn't rationality require identification of one's goals, therefore inheriting the full complexity of value of oneself?

Seconded. We can certainly imagine an amoral agent that responds to rational argument — say, a paperclipper that can be convinced to one-box on Newcomb's problem. This gives rise to the illusion that rationality is somehow universal.

But in what sense is an EU-maximizer with a TM-based universal prior "wrong"? If it loses money when betting on a unary encoding of the Busy Beaver sequence, maybe we should conclude that making money isn't its goal.

If someone knows a way to extract goals from an arbitrary agent in a way that might reveal the agent to be irrational, I would like to hear it.