> This is a true Scotsman’s fallacy. “Legitimacy” of self-interest is fluid and subjective

Legitimacy is the "alignment" question. We can't objectrively judge it, fundamentally, because it's an expression of values: to what degree do the society's system of incentives align with the greater good?

That isn't a No True Scotsman's fallacy, because there are true Scotsmen. Literally Scotsmen. And every other member of a complex society. Including, in all likelihood, you, a person who subjects themselves to laws and employment and fielty for reasons that are a mix of duty and self interest.