I mean 'rational' in the ordinary, indefinable sense, whereby calling a decision 'irrational' expresses a distinctive kind of criticism -- similar to that expressed by the words 'crazy', 'foolish', 'unwise', etc. (By contrast, you can just say "maximizes expected utility" if you really mean nothing more than maximizes expected utility -- but note that that's a merely descriptive concept, not a normative one.)
If you don't possess this concept -- if you never have thoughts about what's rational, over and above just what maximizes expected utility -- then I can't help you.
I don't think we can make progress with such imprecise thinking. Eliezer has a nice post about that.
In You Provably Can't Trust Yourself, Eliezer tried to figured out why his audience didn't understand his meta-ethics sequence even after they had followed him through philosophy of language and quantum physics. Meta-ethics is my specialty, and I can't figure out what Eliezer's meta-ethical position is. And at least at this point, professionals like Robin Hanson and Toby Ord couldn't figure it out, either.
Part of the problem is that because Eliezer has gotten little value from professional philosophy, he writes about morality in a highly idiosyncratic way, using terms that would require reading hundreds of posts to understand. I might understand Eliezer's meta-ethics better if he would just cough up his positions on standard meta-ethical debates like cognitivism, motivation, the sources of normativity, moral epistemology, and so on. Nick Beckstead recently told me he thinks Eliezer's meta-ethical views are similar to those of Michael Smith, but I'm not seeing it.
If you think you can help me (and others) understand Eliezer's meta-ethical theory, please leave a comment!
Update: This comment by Richard Chappell made sense of Eliezer's meta-ethics for me.