Hong King is Chinese territory. End of.
If anyone is unhappy with that fact, they should just pack up and go somewhere else and never come back and everybody will be happier for it.
If you accept that Hong Kong is Chinese territory, you will need to learn how to get results in the Chinese political system. To try and change China itself is egotastical and arrogant for a city of 7m who seem to pride themselves on being different from mainland Chinese.
The first rule of getting things done in China is that you will never be able to strong arm the central government. The more you try to pressure Beijing, worse, the more you try to play up to foreigners to try to pressure Beijing, the less time China's leaders will have for your grievance, and the more likely they will stand against what you want on general principle.
China has moved on since 89. There is simply no need to send in the tanks any more since China has the full range of civil anti-mass riot tools and institutions needed to break up this protest.
Western journalists love to create non-existent BS reasons why Beijing cannot break up those protests as peaceably as any western nation would with a similar display on their own territory, but that's just make believe.
One of the less ridiculous suggestions is that there isn't enough jail cells in HK if Beijing wanted to simply throw the lot of them behind bars until they sobered up. But if needs be, Beijing could simply arrest protestors and bus them across the pond and house them in mainland jails at President Xi's pleasure until each and every one of them can have their day in court. For people who seems almost allergic to anything to do with the mainland, that should serve as a strong disincentive to try Beijing's patients too much.
Similarly, mainland riot police could be bused over at a moment's notice to break this party up, just as western countries have national anti-riot units that are deployed wherever they are needed.
If the protestors think that Bejing is holding back because of how bad it will look if it is forced to use force to clear them out, they are deluding themselves. Sure roit squads being deployed will indeed look back, but nowhere near as bad enough to stay Beijing's hand.
So for the sakes of our HK friends, I hope reason preveils and they start using their heads as well as their hearts.
Rein in your emotion and use your considerable intellect to give yourselves the best chance of getting what you want rather than get thrown into the drunk tank.