Lots of your objection stems from breaking Hong Kong laws (rule of law...being part of China, criminals aren't swept under a rug...).
Worth noting that there is a huge difference between “Rule of Law” and “Rule by Law”: China only has “Rule by Law”, not “Rule of Law” [1][2], because Rule of Law requires Judiciary Independence (hence “having Rule of Law” is incompatible with “being part of China”, as CCP stated explicitly [3]).
To make this concrete, let’s use the recent event of Peng Shuai’s allegation as an example. The accused ex-Premier Zhang Gaoli could be guilty or not, but under Rule of Law—where no one is above law, not even the party or prominent party members—he must go through the same process as other accused. This is the only way to show that criminals aren't swept under a rug for political reasons (such as because Zhang Gaoli was close to Xi Jinping during their time in Shenzhen). Putting the party or prominent party member above law (or behind some opaque process) is NOT Rule of Law.
And a huge disagreement causing the Hong Kong protest is due to deteriorating Rule of Law [4], due to worsening democracy in Hong Kong (the legislative council does not represent the majority opinion). This had been voiced out by a judge of Court of Final Appeal [5] and some prominent lawyer [6].
[1]: https://archive.md/WjWWF
[2]: https://www.swp-berlin.org/10.18449/2021C28/
[3]: https://www.thestandnews.com/china/習近平-法治要從國情出發-決不能走西方-司法獨立-...
[4]: https://www.thestandnews.com/politics/8-4-將軍澳遊行-參加者高太-香港已由法治...
[5]: https://www.thestandnews.com/politics/包致金-香港只享有-類法治-應改變沒有民主也...
[6]: https://www.thestandnews.com/politics/石永泰-亂談法治-會為政權錯誤鍍金
Indeed, the 2021 Report to Congress by U.S.-China Economic and Security Review Commission points out (p. 458 of [7]):
Judiciary Independent in Name Only
Hong Kong’s historically independent judiciary is no longer reliably impartial on cases related to matters the Chinese government deems sensitive, since the National Security Law has cemented Beijing’s right to determine which judges hear national security cases in which jurisdiction, almost guaranteeing outcomes the CCP prefers.
[7]:
https://www.uscc.gov/sites/default/files/2021-11/2021_Annual...Hence, if you wish for Judiciary Independence and Rule of Law of Hong Kong, you would object the NSL, like the protestors did correctly.
This is the reason that comparing the protestors to Capitol rioters, as China did [8], is disingenuous [9].
[8]: https://www.bloomberg.com/news/articles/2021-01-07/communist...
[9]: https://qz.com/1953776/dont-compare-trumps-insurrection-with...
Given the difficulty of maintaining Rule of Law under One Country Two Systems (as Tibet and Hong Kong showed), your hope of Rule of Law would object One Country Two Systems.
Also, before demonizing Two Country Two Systems, have you experienced it firsthand and come to your own conclusion? Do you know what you are disagreeing with?
Given the disinformation campaign of CCP [10], that is, CCP regularly injects disinformation into media (or in this case, deliberately confusing “Rule of Law” with “Rule by Law” in a newspeak way [1][2]), it is hard for Mainlanders to know about Hong Kong and have an informed opinion, even when they moved outside China.
[10]: https://news.ycombinator.com/item?id=20740179