Any defender of settler colonialism in the new world or Australia could say the same thing, and you would be the first to point out why it's bad.

Like it or not, Sinicisation and the destruction of mosques are colonialism and cultural genocide. The massive birth rate drop is also overwhelmingly likely to be genocidal. Even if every report about sterilisation is false, forcing an ethnic minority to have 90% less children than they were before is a genocidal policy: they want less Uighur children to exist.

Anyone who cares about the self-determination of indigenous peoples would naturally care about this too. China doesn't become ontologically evil because they do some bad stuff. No socialist project should be above critique. China is not our football team.