If they're basically going to be steamrolled by a rather unsubtle up-and-coming superpower, perhaps they have no choice. In fact IF violence is all you're left with (and that does seem to be the case as legal recourse is blocked) then violence is necessary.
The CCP is not backing down until it has borged HK.
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.
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.
It's far from perfect but it's infinitely better than on the mainland.
Nothing justifies "resorting to violence" in HK today. The violent actions along with anti-Chinese displays are in fact counterproductive because they push the central government to tighten the screw and unite the mainland's public opinion against them.
Many of these protesters have no democratic culture themselves. Anyone who disagrees with them is wrong and an enemy that must be fought by any means.