The key word here is "see". The problem is that we mostly see what we're primed to notice—which is basically whatever we most dislike—and we simply don't see (or don't weight as heavily) all the cases that don't feel that way. This creates a feeling of "every" or "always" (see https://news.ycombinator.com/item?id=23835843 in this thread), which is a true statement of what you've seen, but only because your seeing is extremely conditioned by your passions on the topic. (I don't mean you personally—we all seem to have this bias.) People with opposite passions see literally the opposite picture. Moreover, the degree to which the picture you see feels unfair and unbalanced is a function, not of the raw data stream, but of the intensity of your passion, regardless of which direction it points.
For evidence, if you search my comments you'll find examples where I've admonished users for flamewar in the opposite direction, as well as for flamewar on other topics, including nationalistic flamewar about other countries (India is probably the second most common case; Russia was up there for a few years and still flares up at times).
Can you do extra work for free, that will be full of uninteresting spam, that no one will ever read, so that I can I win some sort of imaginary war against the CCP/HN boogeyman?
I don't mean to pick on you personally!—these are common feelings, rooted in cognitive biases we all share. But the patterns they claim are not even close to true, so anyone who wants to be convinced by evidence can just look at HN in the first place.
Beyond that, there's plenty of transparency available through HN Search and the moderation record of https://news.ycombinator.com/threads?id=dang. Anyone who looks through the record can find numerous examples of us moderating opposite views in exactly the same way, if they want to. The litigious type of user tends not to want to, and although that group is small in numbers, their capacity to consume moderator time and energy is prodigious. It steals a lot of resources away from other users and from the things we need to be doing to improve the site in general.
By the way, I don't claim there's no moderation bias. How can we know what unconscious biases we may have? I'm just saying that certain stock allegations about it are incorrect and have clear explanations.
There isn't any class of things we do that is secret, though.
If you see things critical of US/Europe/Canada sitting and not strongly moderated - that's because people can usually hold rational and informed discussion on those subject. (btw this one is sitting as well? is it not?)
I don't see the same when it come to China, it just gets flooded by propaganda from both sides, and it devolves into a flamewar. People start accusing each other for being spies and shills, and wishing ill on an entire people because of where they're born and how they happened to be governed. And that doesn't belong to HN and should be moderated, if you like information or discussion that conform to your existing bias you can definitely participate at /r/worldnews.
Can you present the evidence of manipulation? The data is in the open.