I agree with you. The beating of the drums from Beijing is all about unity and normalcy. The only threat Hong Kong is to Beijing is the ideas of freedom and democracy. And if those ideas ever get into the heads of the mainland then who knows what may happen. So Hong Kong needs to be taught a lesson. It's just a matter of when and in what kind of form.
The Communists successfully hijacked the existing political culture of China, pre 1949 - bowing to the imperial center. They did not change it, they - Mao and the politburo - merely took on the mantle of it for themselves. That is a deep cultural trait among the Chinese people, with many centuries backing it up. With that the Communists have successfully also hijacked the mantle of “Chinese nationalism”. They are the imperial center in new clothes and masses of mainlaind Chinese would not argue with it.
Hong Kong is a different story. They - their brief life as a British colony, broke the mold of the political culture of the old imperial center. And they do not want to go back to it.