Your principles seem to be summed up as: so long as someone is speaking their opinion respectfully and in good faith, it matters not what that opinion is; and that the defense of this necessitates a generous presumption of good faith.
We must acknowledge that HN carries a substantial degree of influence, and consider how to responsibly wield that influence. The readers here are a lucractive demographic - generally we are an educated, wealthy, and politically engaged group. As propaganda becomes more sophisticated, it's likely - if not inevitable - that it will target us. It's the responsibility of the moderators of our online spaces to protect us from propaganda, else Hacker News is used as a weapon, to ill or to good - a possibility that you must be aware of.
Distinguishing between propaganda and genuinely held positions is difficult, and approaches impossible as propaganda technology becomes more sophisticated. For this reason, I think it's reasonable to suggest that certain viewpoints are simply not welcome on Hacker News. There are some easy examples: racist or sexist views being one of them. I presume that someone expressing racist viewpoints, no matter how eloquently stated, is not welcome to do so on Hacker News. Then there are more difficult problems, which stem from a complex web of related judgements. To address these, I suggest reflecting on your own moral principles, and considering what ideals are worth protecting in the face of propaganda. In the case of Hong Kong, the ideals at risk here are the right to self governance. And there's little question that the alternative Hong Kong faces would be tragic - China is demonstrably a country with little freedoms afforded to its people and large-scale human rights violations being carried out all the time. The demonstrators in Hong Kong will not be let off easy for the risks they're taking, should they fail.
In short: like it or not, HN is a tool which will be wielded by oppressors, and will likely be an effective tool at that. Identifying oppressors is difficult but identifying the values of oppressors is easier.
Also worth note: HN is inextricably linked to YC, which has financial investments in China. If you don't want to be views as having a pro-China bias, you need to put in extra work to remove the foot from your mouth.