As we saw after the invasion of Ukraine, the West can mount a swift, concerted and effective response, that deals a lot of damage to the offending country's economy. I'm sure that evidence of Xinjiang crimes will invoke the same kind of decisive action.
While I distinctively recall non-westerners arguments on HN about how "Russia treats Ukraine with kids gloves" or "America did bad things and therefore it is OK for Russia to invade Ukraine" (somehow punishing Ukrainians for American history). Or how "since countries around Ukraine did not locked Ukrainians inside, they are bad nah, I will not talk about how our own countries treats refugees nah".
"It is unfair to provide material support to Ukraine, unless you are willing to also invade and occupy China over their crimes" is not particularly strong argument. Especially not if the fully expected corollary is "but if you do what we now demand we will blame you for international aggression".