This is a gross misinterpretation. What the protestors actually wanted was:
- For the UK to grant BN(O) holders citizenship to show that they are no longer bound by the Sino-UK Joint Declaration.
- For the US to revoke Hong Kong's special status (the Hong Kong Policy Act).
BN(O)s are already British Nationals (hence the 'BN'), what they're missing is Right of Abode in the UK.
This is why the recently proposed BN(O) changes are quite significant.
If this comment is not flagged, I am interested that specifically what autonomy is taken from Hong Kong so that this "un-nationalism" happened?
Then there's the case of the missing booksellers [2]. Another clear violation of Basic Law and the handover agreement which enshrines freedom of speech and of the press in Hong Kong (again, a violation of the rule of law).
Then there's the fact that the high-speed rail station in Kowloon which connects to the mainland is guarded by China Police, who are not allowed to operate in Hong Kong under, you guessed it, Basic Law. [3]
Not to mention the pro-democracy elected officials not being allowed to assume office. [4]
The list goes on, and on, and on. The fact is the PRC agreed to treat Hong Kong a certain way for a certain period of time, and it has failed to live up to its obligations. It has for years now been boiling the frog, so to say, whittling away at the freedoms guaranteed to the Hong Kong people for decades before, and decades to come. With this, they've lurched over the line.
[1] https://www.theguardian.com/world/2017/feb/01/chinese-billio...
[2] https://www.nytimes.com/2018/04/03/magazine/the-case-of-hong...
[3] https://www.theguardian.com/cities/2018/oct/04/high-speed-tr...
[4] https://www.theguardian.com/world/2017/jul/14/hong-kong-pro-...
I sincerely doubt that had Beijing given Hong Kong the autonomy it committed to, you'd be seeing this kind of action on their part.
It didn't need to be this way, but the CPC cannot tolerate anything that might be perceived as an attack on "national unity" (and I use quotes only because "national" as defined by the CPC extends into the sovereign land of a number of countries including (at least) Taiwan, Indonesia, Malaysia, the Philippines and India).