Earlier quoted context omitted.
As a Japanese, I will mention that I've seen Japanese people correct each other on this, both in private and in public. Its because we might get the meaning by context, but if you pronounce it wrong, it sounds very strange in that context where its clearly wrong... To default to an assumption that this is due to racism / cultural gatekeeping says a whole lot about your world view and perception about Japanese people…
As a foreigner living in Japan, I'd like to take the opportunity to let you know that it's not ethnocentrism, but that Japan is for the most part quite xenophobic, and racist. It's common to hear Japanese folks make fun of other people's accents in what should be obviously extremely inappropriate settings, like at work, for example. The fact that you consider this ethnocentrism furthers the point that xenophobia and…
> My wife points out when I make mistakes in Japanese, but I ask her to do so. If a coworker or stranger were to do so, it would be embarrassing, and that's the difference that matters.
Another great point. In my experience, the very best language lessons are from casual interactions when a stranger makes a correction to my foreign language when replying me, but not in a derogatory manner. Most of the time, you can tell they are trying to be subtle and give you a helpful hint.