This attitude is unfortunately the problem.
There is no such thing as HK people, only the country, it's allies and it's enemies. HK should not be governed by the "HK people" anymore than SZ is governed by "SZ people". A decline and fall of HK is a failure for China.
The central government is the sole responsible party when it comes to controlling the city, hiding behind excuses of "letting HK people choose" is the exact reason why far right terrorism has become an issue. Even more pathetic is hiding behind the excuse of "honoring" of treaties with genocidal aggressors, which not only should have no legal power, but they have themselves already broken the treaty by interfering into HK affairs when the deal called for non interference on both sides.
People are the way you treat them. The mainland is at fault for separating itself from HK for too long. Beijing didn't want to show itself mass murdering the cockroaches, but the destruction of Xinjiang terrorism already showed that more humane methods of reformation exist. And even if they have to resort to executions, just look at what's happening in other countries, like US and Israel. Such things happen all the time and are a fact of life. Some people would bitch about it, some people would cheer for it.