The USA itself has by far the highest incarceration rates of any developed country, over 5x that of China. In certain demographics this rate is as high as 1/3. By the numbers this is more than what the Uighers experience in China, and e.g. Europeans can and do criticize the USA relentlessly for it.

If you're wondering how people in China justify the government's treatment of the Uighers, the answer isn't that they have different moral instincts than you. They justify it to themselves in the exact same way you justify America's incarceration rate to yourself. (If you're thinking that it's different, because what they're doing just feels dystopian and evil, while we're just doing the best we can, obviously realize that this is pure tribal bias. Others might have the reverse associations.)

Of course, what I am doing is textbook whataboutism. But that is the correct response to a claim that some foreign country is uniquely evil.