The problem is that people aren't ideal rational agents. Our collective reasoning tends to be heavily biased by the environment, and that there are actors who abuse this (by injecting ideas that indirectly help their agendas) for their personal gains. And in China's case, they want to undermine freedoms, including freedom of speech.
We can consider ourselves as "rational, critical thinkers" all we want, but we aren't as there are myriads of ways we're gullible in one way or another. Plenty of examples in our history books.
Still, I think that free speech is still more important, as it's the only way for a society to recover. With freedom of speech, an antidote (for a lack of better term) can eventually be found and injected into the public discourse, without it the future looks bleak.
The way I see it, we need to encourage improvement of education on social sciences, human psychology, game theory and so on, encourage critical thinking but forewarn of all possible fallacies, and hope that it will be enough and that the inevitable counter-reaction won't prevail and undermine the effort.
