Of course it's frustrating to encounter inflammatory comments that are based in ignorance. But if you respond like this, you feed those comments and give them greater credibility, while discrediting the very side you're trying to defend.
If you know more, then a better way is to share some of what you know so that others can learn. In any case, if you post here, please stick to the site rules regardless of how wrong or ignorant other commenters are or you feel they are.
My apologies if it came out wrong.
If you post in the flamewar style, everyone's going to just go rigid and fire on all cylinders. This mechanism works the same way regardless of what the topic is, and regardless of whose position is right or wrong.
I think the HN's algorithm also contribute to the problem: the fastest and most upvoted response leads the discussion, and normally not the most valuable.
People look down on Trump and ridicule him endlessly when he spews bullshit about things he knows nothing about. But if you spew bullshit about China, you get lots of upvotes.
And if you dare to speak the truth and the nuances about the situation in Hong Kong, you get downvoted to oblivion.
EDIT: Case in point, downvoters! Go ahead, show me you know something about China and Hong Kong.