Let me just ask one question: how do you see this end?
A lot of the commenters here feel the unrest in HK is isolated and therefore has no ill effect upon China. While the former is true for now, the latter is not.
Up until now, the HK riots have had a galvanizing effect on the Chinese people, but without an endgame, this will eventually become cynicism.
Meanwhile, the patriotic citizens of HK will continue to have their lives disrupted, sometimes even put into physical danger. Some are already questioning the Central Government's inaction, and this number will inevitably swell. If Beijing waits too long, it will lose the good will of the patriotic citizens.
It doesn't have to end. As long as it doesn't reach any of the strategic red lines I've stated a while ago, it is not necessarily a bad thing. You have to look at the bigger picture. The West led by the US has long treated any so-called "challenger" civilizations with great suspicion. There are no way for a rising China to evade the scorn and suspicion of the US led West. Especially now, even if China stopped growing, it will still no be enough. For them, they want to see China NEVER again have the possibility of challenging them, ever. Just like how they treated the Russians, after the fall of USSR.
This is why the US led West will pour energy and resources into containing and sabotaging China. Containment alone is extremely difficult in the long run (we can discuss why in another thread). This is why they will put resources into sabotage actions. This is a given, not an if.
Again, the above means that a lot of Western resources WILL BE put into sabotaging China's stability. Since containment alone is not going to work in the long run. In any sabotage mission, Hong Kong would be a low hanging fruit, both for terrorism and for "Occupy"-type of unrest.
Suppose China act immediately on Hong Kong, get the whole thing over and fight the necessary diplomatic battle with the US led West, and get this whole thing over fast. And Hong Kong unrest is put down, and tranquility restored. So what? Does this really cure the root cause of why such an unrest will happened in the first place? IT WILL NOT. Because that which fuels it, is the endeavor by the US led West to carry out sabotage mission to bring instability within China. If such endeavors/intentions do not die, there will always be sabotage to spark unrest. HK is just the low hanging fruit. If even the low hanging fruit become difficult for the US led West to initiate an unrest, what do you think will happened? Do you think they will simply give up? NO, the US led West does NOT give up on such things. In fact, if they faces obvious obstacles, they will pause, rethink, and improve their games. So that the next sabotage mission will be more intense, more effective and more radical. This is not in the interest of China.
This is why I think the best scenario is for Hong Kong unrest is to go on like this, as long as it doesn't cross the red lines. This will become a draining pit for the sabotage mission of US led West. The game of draining pit is difficult, it has to take "the middle route". This means that it has to be sufficiently rewarding to draw the other side in. This is why I think the HK government is correct to show weakness against the protesters. This will draw the US in.