[GCSAQCMIYI]

I certainly agree that everyone's values are ultimately arbitrary, but that's pretty far outside of this discussion. Most people are self-interested, and the person I originally replied to was talking about normal people. "This phenomenon is root of all evil in modern day America. People identify with political parties as though they are sports teams."

[crispinb]

That's fair enough, but I think the conflation of self-interest with rationality is so ubiquitous (and like most official ideologies, dangerously mistaken) that it's worth challenging when it arises. Or at least to the extent permitted by one's energies and everyone's good humour.

(I don't btw agree that values are entirely arbitrary, but that's a discussion for another day).

[GCSAQCMIYI]

I'm curious why you see it as "dangerously mistaken". What is the danger in making that mistake?

[crispinb]

It's a longer discussion than I have time for now, but in short: it creates ethically worse people (unnaturally selfish) without them being any more 'rational' (just as subject to biases as ever). And it creates worse societies, eg. the US. The two feed back and forward to each other, making for a downward spiral very hard to arrest.