Few to none of the posters here think the riots in HK affect the rest of China much, at least directly. It does have implications for China's appeal in any other one-country-two-systems framework such as potentially Taiwan. And it does have an effect on China in that Hong Kong is part of China, so if this hurts Hong Kong (or its integration with the rest of China) then this hurts China.
These riots do have an immediate negative effect on the average person in HK (especially those less well off, live in the affected areas, or who don't agree with the rioters) who have their peace, everyday lives and freedoms, property and personal physical well-being threatened, harassed, and attacked by the rioters and their co-conspirators. These are real life difficulties that affect some posters' families, friends, and hometown, it has nothing to do with their egos or missing anything on a strategic level.
I disagree to your notion that it has (I presume you meant negative) appeal in one-country-two-systems framework for Taiwan. In fact, I think this is a good thing for relation with Taiwan. This is because so far, the HK government has basically handled the protests and riots effectively, at least to the point that PAP/PLA don't have to be called into Hong Kong. Yes, of course there are some immediate negative appeals, but as time goes on and the dust settles, this will be a great evidence that the O-C-T-S works. Things will always get worse before it gets better. In fact, had Hong Kong not go through such an ordeal, it would still be an unsatisfactory example of O-C-T-S in the eyes of Taiwanese, because it is untested. Once the fever dies down, it will emerge as a great example of how O-C-T-S actually works.
As for your notion that since Hong Kong is a part of China, anything that hurts Hong Kong, hurts China too. Well, I would say that it's not very meaningful because for any country the size and power of China, regional and local unrest and problems is bound to happened. This is especially true in a world where the predominant power (the US and the West) perceives China's rise as a threat. China is bound to brace itself for western sabotage and adversarial actions, this is to be expected. I don't think we should look at this purely in a negative light, especial since we are Chinese (Chinese culture always looks at both side of the coin, 福兮祸之所伏,祸兮福之所倚). In fact, I am grateful that such a riot/unrest manifests itself in Hong Kong, instead of Beijing or Shanghai.
I don't want people to get upset about such riots because it is actually happening in the least hurtful place in all of China. And given the current geopolitical situation China is in, such a problem will happen. I am happy that it happened in HK instead of elsewhere in China.