The United States doesn't have any right to speak from a position of moral authority in the world. We're responsible for more death and destruction that anybody else in the world. We would only be hurting ourselves if we stopped trading with Hong Kong, as trading improves our economy and the friendly relations are a determent to war.
No, it is my belief that the US should not stop doing business with Hong Kong. Although what the city of Hong Kong is doing is terrible and unacceptable, to stop doing business with a major city in China would only be detrimental to the US, and at this time, the US needs all the help it can get.
The United States has slaves as well. So does every country on earth. The only question is to what extent the state is responsible for sponsoring it. The United States has its own human rights abuses that other countries could point a finger at. If we refused to do business with every country that did terrible things, we wouldn't even be able to do business with ourselves.
It is my opinion that no, the US should not stop doing business with Hong Kong. Regardless of their practices or how things are in their country, I believe that the US needs to look out for the US first and stop worrying so much about other countries. Sometimes we're just shooting ourselves in the foot or making it more difficult for our own citizens when we get too involved in other countries' affairs.