A lot of westerners have been brainwashed for literally decades by their media that usually tows the US propaganda line when it comes to China, Russia, or any other nation that does not follow US orders or US interests.
I don't think it's helpful accusing people you disagree with as being brainwashed, except for very exceptional cases like North Korea, where people live in fear of them and their extended families being imprisoned and tortured over otherwise innocent comments.
The fact that a lot of media opinion pieces in North America and Europe may be critical of the CCP does not mean that the local populations are brainwashed. Pro-CCP opinions can be easily accessed. There's no need to use a VPN or dodge some sort of state-imposed block. There's also no state-based punishment for agreeing with the CCP. Also, historically on issues like Taiwan there were actually a lot of pro-CCP opinions even in the mainstream media, largely because at the time the view was "better not annoy China, just pretend it's not an issue, don't sell arms because it's the wrong time", etc.
Bringing the discussion to the topic at hand (Hong Kong), it's important to remember that disagreeing with young Hong Kongese/the protesters doesn't mean they're incapable of rational thought. They have easy access to a much wider body of media than people in mainland China do. There are lots of pro-government TV stations, radio channels and newspapers in HK. Also, ironically, this upsurge in political awareness is partly down to the HK government pushing critical thinking classes years ago because they were worried about rote-based learning.
If a discussion can largely be reduced to "X is brainwashed, therefore I win", it's not being held in good faith.
Just like their proposed Covid-19 investigation, perhaps Australia will outdo US and propose to lead an independent investigation to certify that Hong Kong is an autonomous country subject to the Queen of England. Quite Plausible. 
