Yes but a Westerner would hardly be the objective judger of such gulags/guantanamo bays of China. That being said if too many people were being sent to prison in China, unjustly, they'd have another revolution.

The fact is that even if evidence was revealed they had absolutely 0 gulags, or whatever it is you're claiming, it would not do much to silence anti-China sentiment. The presence of the gulags are not falsifiable, since opponents can always claim fabrication by the authoritarian regime. The only objective way is to defer to the majority of Chinese citizens, which currently approve of their government.

There's little point in arguing if the communist party is a party of saints—they'll always be doing something wrong, and they definitely are. The question is do they have a legitimate control of China? That's something only someone under their regime can answer and fight for, not a Western imperialist.

is there a difference in human suffering based on color of skin/cultural background?

In theory, no, but in practice, there's a question to the underlying motivation and ulterior motives if one is fighting for another's rights more than that other person is.

For example, to an American the invasion of Iraq may be officially an Operation for Iraqi Liberation, but to an Iraqi it may seem like control of OIL was the motivation. From a third party perspective you have to assume an American is motivated in self-interest, so if they seem more interested in the "liberation" of another group more than that group is itself, your duty is to question that motivation. The primary purpose of the US government is to serve American interests, so any reasons it gives of altruistic or justice-serving intent can be immediately thrown in the trash. I'm saying this as a tax-paying American citizen by the way.