A friend of mine who is from the mainland but spent most of their life in the United States went to HK a few years ago. They told me that traveling on a PRC passport really set off the immigration folks, and that even day to day folks were fairly rude -- to the extent that they attempted to mimic a Taiwanese accent.

I think it's unfortunate, but understandable, that there's a certain amount of contempt for mainlanders beyond "love the people, hate the government" as the problems go beyond the government (e.g. affluent mainlanders stocking up on 'safe' supplies from HK).