Invocation of Whataboutism is an easy cop-out to never have to look one's self in the mirror. It's used by people in glass houses who only want to throw stones at their neighbors.
It's also not applicable here since the grandparent already did a relative comparison of China with the supposedly better "western track record", so this comparison warrants a response.
No, the argument is more like saying that Germans calling the allies as beasts for what happened to Dresden should also look at what happened to the Jews.
The difference, in case you didn't notice, is that while racists are indeed racist and people against racism aren't, here the two sides are equally bad.
To say X has the moral high ground or X does not have the moral high ground is a variant of "argument from authority" and it's opposite as an ad hominem. It doesn't have any bearing what so ever on the issue at hand.
Except in Hong Kong. Obviously liberty for their citizens is the one to pick so the US easily comes out on top.
However if you pick percentage of their population they imprison or civilian death toll in expansionist/imperialist conflicts? Or scope of global assassination programs?
But a point by point comparison is not really the point here is it? Obviously the American system is more capable of checks and balances than the Chinese system. That arguably makes the massive failures to use them worse. We disagree on what the word "trying" means regarding a state's actions I suppose. That seems fair, it's a fuzzy idea in this context.