The “self” in “self-hating ____” is not really you. It’s the version of you that other people think you’re supposed to be, based on what you look like and where your ancestors came from. “Self-hating” is an accusation of not living up to stereotype.
Rejecting, ignoring or simply not taking the necessary years to learn the culture and language of your grandparents is not an act of self-abnegation, because your grandparents are not you, and the version of you that you’d be denying is from an alternate dimension where language and culture are passed down genetically.
You’re born in suburban Michigan to parents who both speak English. You grow up around friends who also speak English. You half-heartedly study Spanish in high school. What part of this picture inclines you naturally to know Vietnamese, Korean, Polish, or any other language, just because your last name is not Anglo?
The accusation of being inauthentic or self-hating for not embracing the culture of one’s ancestors is seldom leveled at people in the ethnic majority. Only minorities are made to feel they must justify their existence by contributing some ethnic spice to vanilla Americanism. No one calls Dwight Eisenhower or Andy Richter self-hating for not learning German.
Yes, learning a second language is always good, and a language that someone in your family already speaks may seem to be a natural candidate. If you’re not burdened with the expectation that your whole identity is wrapped around your minority ethnicity, it makes sense to make progress, however meager, toward a second language that perhaps you have a unique amount of access to. But as a nominal member of the group whose language that is, taking a step towards learning it doesn’t mean going from 0 to 1. It means going from -100 to -99.
I don’t look very Japanese, and most people in Japan when they hear my last name assume I got it by marrying into a Japanese family. That is, I’m a gaikokujin learning Japanese, and my account balance on language skill is positive. When people hear that it’s actually the last name I was born with, they have a moment of “oh, so that’s why…” and their perception of me changes. The explanation for my language ability becomes genes rather than effort and I transform from mildly proficient to a curiously deficient.
It might have been easier for me, and I suspect many minorities, to simply avoid “their” language and avoid putting that negative balance on the books.