Many people from Hong Kong and Taiwan don't want to be associated with the mainland Chinese. I have friend from Hong Kong and I never thought one ethnic Chinese could hate his own kind from the interior. Also, when the pop group S.H.E. were called Chinese by the interviewer, one of the member's said "I'm not CHinese, I'm Taiwanese."
As to the Chinese when they call me Loa Wai, I call them Loa Zhong- just to be fair.