They don't need to. If only 1% of the people are able to access censored content and therefore hold censored ideas, the majority will treat them as crazy pariahs.
It's the same mechanism that makes us consider the 1% of flat earthers crazy. Sadly the mechanism works based on how many people believe a thing, not whether it's true, so it can also block true things if only 1% of people believe them.
We don't think that people who think there's a bearded man in heaven are crazy, even if that's crazier than thinking earth is flat.
We don't think they are crazy because they are not 1%, they are majority.
Most people think flat earthers are crazy not because they proved them wrong. Just most people around them think flat earthers are crazy and that's enough.
There is no way to prove that the earth isn't actually flat but every observation conspires to make it look round. For instance some flat earthers say that the atmosphere reflects light in the exact way that makes it look round.
Take any phenomena on a globe earth, describe the exact same thing in flat earth coordinates and then say that everything weird in the equations is a new physical effect you just discovered.
That's a void argument.
If every observation conspires to make it look round, it's round because observation is all we have. Refusing to accept observational evidence that forms a coherent explanation is either anti-science or anti-definition-of-words. This justification for flat earth exits the realm of scientific inquiry and enters the realm of Cartesian evil demons, a hypothesis even Descartes rejected.
We think flat earthers are crazy because it is a fairly trivial thing to prove them wrong. If you believe something that is that easily disproved AND widely understood to be so, there is clearly something wrong with you.