I don't understand for example, when a Japanese person gets mad if someone guesses that they are Chinese.
I mean, wtf... We can't tell if a white guy is Irish or Scottish... So we shouldn't expect others to either.
And alot of Ethiopians at my job refer to African Americans as black people, but they themselves prefer to be called Ethiopian. And they want to separate themselves from "regular" black people.
I understand if some ignorant redneck calls you Chinese in a demeaning manner, which happened to me, and you tell him to go fuck his wife and sister, but I don't think we should expect other races to be so keen to nationality differences.
I sure don't want to waste my life learning the difference between a Ganian and a Nigerian.