If you reject the idea that people are intelligent enough to think about politics for themselves then you reject the idea that they're intelligent enough to govern themselves. Democracy and free speech are intrinsically linked.
Question: Why is this a threat to democracy, but previous censorship wasn't? There's always been an expectation of truthfulness in communication: We don't allow people to go around claiming that Pepsi causes AIDS, or cures cancer. You're not allowed to claim you're collecting for a charity, and then keep all the money for yourself. I doubt you'd be terribly okay with me claiming that you're a murderer and asking how…
People are not defending fraudulent communication. They are observing that the same factors that make audiences vulnerable to misinformation affect the censors and the process by which censors determine which information is harmful.
If we had a test for truth or sincerity we could use it to determine which information was false or put forth in bad faith. We don't, so any person who acts as an information gatekeeper could be one of those people who is lying or deceived and they would then be able to corrupt the discourse by censoring the information that exposes their lies or misunderstandings.