Except there is no "legitimate argument" here. Just throwing emotive words around and hoping some of that sticks.
If you feel like the matter of "a certain minority" in China is any way relevant to what Nazis did, then maybe you wasted your time at school and should open up a history book and look up what exactly was the context of what Nazi were doing to Jewish and Romani people.
As distasteful as China's actions might seem to be, their end goal is assimilation, unlike Nazi's goals of isolation and physical extermination - I'll refer you to the fate of "The Association of German National Jews" on this one.
Westsplaining is just a phenomenon of certain people rationalizing their own xenophobia without actually caring about the principles they talk about so much when trying to take some moral highground. Which is why the "history" (as if it happened too long ago or seized to be the case now, yeah, right) of western civilization dealing with similar issues is "irrelevant". This term should be in the "see also" section under "looking at the speck of sawdust in your brother’s eye and paying no attention to the plank in your own eye".
You can condemn all you want, but I don't personally see why objectively China should deserve to be treated any worse than say United States, that had fared far worse in similar situations, like it's reaction to 9/11 with torching a whole other fucking side of the planet, or it's ICE detention camps - the last one being actually much closer to Nazi isolation policies than China's assimilation policy of Wahhabism-leaning minorities.