The Chinese government apparently has violated agreements made with Britain concerning the transition of Hong Kong from British to Chinese rule. Those violations concern the end of freedom for the people of Hong Kong insofar as freedom is found within self-government of Democratic forms of government rather than authoritarian rule and Chinese authorities are ending several basic planks of democracy in Hong Kong.
Arresting pro-democracy demonstrators and holding them indefinitely as well as exporting them to distant Chinese jurisdictions for adjudication are a couple of items people regard as human rights violations. That is, government with the consent of the government and trial by a jury of peers, habeas corpus etc. are necessary for a free people to feel free with the best government so many people can use to remain as free as possible.
The Chinese government has a tradition of crushing human rights these days in order to further communist rule that is of course also liberalizing business to a certain extent. The west is partly at fault for building up the Chinese economy with technology transfers and financial investment that swells Chinese military spending and the aggressiveness of Chinese politicians seeking to expand their power peripherally so far as they can. Hong Kong is something of an innocent bystander being run over by growing Chinese economic power and neo-authoritarianism that isn’t looking far enough beyond purely materially and atheistic ideologies to find a greater spiritual foundation of freedom for its people that might be a good influence on decaying western moral norms as well as its own.