sasum
You can't have your cake and eat it too. Hong Kong benefits immensely from its autonomous position in regards to the Chinese government, so they don't want to disrupt the status quo. The protests have revealed HK to be a national security issue for the Chinese government, so they want to create laws to make sure HK isn't used as a center of political dissent. These two ideas are contradictory with each other, so a law like this was inevitable.
>And I'm not sure how Hong Kong's previous autonomy (or any other freedoms) would come at the cost of the PRC's sovereignty?
I'm not sure if you understand the original impetus of the extradition bill. Here's a good Twitter thread that details the provisions: https://twitter.com/DanielDumbrill/status/117502034599824588...
To answer your question, if criminals are able to easily escape China into Hong Kong, that fundamentally weakens the justice system. HKers and mainland Chinese move between HK and the mainland constantly. It would obviously be a failure of justice if you could go to a city within your country and encounter the man who killed your daughter. A similar law exists within Puerto Rico, a US territory. This is the bill that originally sparked the protests.
Recently Beijing passed the bill we are talking about that also gives them much more power in terms of being able to imprison HKers that try to subvert the government. This can be seen as a response to the protests, whose leaders have been revealed to be funded and supported by foreigners. China's sovereignty is absolutely threatened by protests and riots that seek to destabilize Chinese places of power, like Hong Kong.
>As long as it's happening openly, I can't get too upset either way
If you can't get upset about the US meddling in Chinese affairs, then you can't get upset about China trying to stop internal subversion. Not to mention, it absolutely doesn't just happen openly. The US has a long history of covert regime change operations. This happens completely undemocratically. Here's a short list: https://en.wikipedia.org/wiki/United_States_involvement_in_r...
I mean, just look at the hysteria surrounding Russian involvement in US elections. Rumors of Trump officials meeting with Russian officials has set public discourse on fire for years. And yet, it's unreasonable for China to oppose Demosisto party leaders who have openly met with US officials. I'm not trying to use whataboutism to deflect, I'm trying to paint an equivalency between the situations of these two countries.
>where did you develop these beliefs?
I'm fairly left leaning. China is a leftist country. I know China isn't perfect, but you can easily rationalize their decisions as being made by a government that cares about its people, not power-mad evil dictators as most people would have you believe. If you're interested in learning more, I would recommend reading Blackshirts & Reds by Michael Parenti. https://mltheory.files.wordpress.com/2017/06/michael-parenti...
For example, the majority of people would agree that they do not want their taxes to be raised (https://news.gallup.com/poll/1714/taxes.aspx). Those same people might not like the ramifications of that, but that wouldn't necessarily change their opinion.
Back to HK. The existence of HK as a semi-autonomous region that is still part of China provides a great way for foreign powers to extend their influence into China's domestic affairs. In this scenario, the US clearly has its hand in HK domestic affairs. US leaders are meeting with protest leaders. US organizations are funding protests. Flip this with domestic affairs in America, and you'll see that there is something deeply wrong with this picture. Although it isn't 1 to 1, imagine if China were funding BLM protests and inviting BLM leaders to Beijing.
I'm going to add a few links which support these claims if you were unaware. You could find some more yourself if you'd like:
US role in Hong Kong protests - https://www.workers.org/2019/06/42820/?fbclid=IwAR2ZjOUSl2Bt...
US Senator Ted Cruz visiting Hong Kong - https://twitter.com/CarlZha/status/1182937896795246593
American Gov’t, NGOs Fuel and Fund Hong Kong Anti-Extradition Protests - https://www.mintpressnews.com/hong-kong-protests/259202/
Sidenote: I am American. I have learned about Western-style "freedoms" and find them very contradictory with America as it exists today. For example, the American rate of incarceration is the highest in the world, surpassing even the highest rates of incarceration of Stalin's USSR. Obviously, not everything China does is good and not everything America does is bad, but I'd encourage you to take a more critical eye to any mainstream Western sentiment on foreign countries, especially when that sentiment usually results in thousands being killed.
And to expand on your point about wanting to empower self determination, then you should stand with the HK government against foreign influence in HK domestic affairs. There is ample evidence of the United States pumping millions of dollars into the protests. The leaders of the protests have met with US officials to get their support. This is not normal. Imagine if news came out that BLM leaders in certain cities were meeting with Xi or Putin, and receiving millions in funds.
Not to mention, HKers DO NOT want independence. In a recent poll only 20% of HKers desire independence.