The Chinese government doesn't play fair, and the West has been letting them get away with it for decades. They take full advantage of open markets available in the rest of the world, but close their markets to outsiders; at best, outsiders can get a piece of the action, but only through the oversight and partial ownership of a local company. The idea that China is still a "developing nation" and should have special status and privileges is a joke.
While I won't claim that Western nations don't have issues with censorship and freedom of speech, the Chinese government punishes foreign corporations (economically) that say anything critical of China or its government. The Chinese government exports its propaganda and censorship policies through informal economic sanctions.
I'm not particularly interested in allowing an authoritarian government that pushes pervasive propaganda and censorship to become the next world hegemon. (I'll freely admit that the US is no saint in that role, but I think it should be obvious and defensible why I'd prefer the US in that position rather than China.)
Note that this is all about the Chinese government. I have no problems with Chinese people; by and large, those I've met on my few trips to China (granted, my last trip was over 10 years ago) and those I've met who travel to and live in the US have been good, friendly, intelligent people. It's perfectly reasonable to be against the constant, widespread actions of a foreign government without being branded a xenophobe.