Some people make it easier - on many occasions you'll see someone discussing a subject but first disclosing their relationship, such as an ex-Google employee commenting on a Google-critical article. If a Chinese party official came to HN to express their views and disclosed themselves as such, I would welcome them to express their opinion here. What I'm concerned about is commenters with undisclosed affiliations writing manipulative comments which help prop up an oppressive state.
How do you propose to do that? Clearly one must look for evidence. When evidence shows such abuse, we ban the account. Far more often, though (and I'm understating things when I put it that way), evidence shows the opposite: the user was expressing their genuinely held beliefs. Should others be allowed to denounce them as astroturfers, shills, or spies, based on nothing but how strongly they disagree? On HN the answer is no. That follows from the values of this site, and we have a rule in https://news.ycombinator.com/newsguidelines.html saying so.
Isn't that the point of a discussion forum such as HN?
> I think it's reasonable to suggest that certain viewpoints are simply not welcome on Hacker News
I disagree that contrary viewpoints "no matter how eloquently stated" should be purged. Let them stand or fall on their merits.