The grounds for the modern idea of "asians are so racist" feel like mostly a kind of surprised reaction to the racism and discrimination still preservering inside a supposed ethnostate. It's mostly because we take western ideas of "racism amount" to a different context and get surprised that "pan-asian unity" isn't a thing considering they "pretty much look the same" and that people that we'd consider essentially the same "race" as Japanese people (Koreans, Ainu, and even Burakumin) still are discriminated. The shit you're talking about is mostly an modern internet idea from white people feeling foreign in a foreign land that has dictated most discussions among nerds.