Every society that grows past the point where people are largely self-sufficient needs some way to settle on common truth if it is to remain stable. But it also needs a way to update what it considers to be true, because sometimes what it decided is true turns out to be wrong or later becomes wrong as circumstances change.
That update mechanism needs to have some friction, though, so that you don't make too many wrong updates.
Free speech is a mechanism that helps with the updates, and up until maybe 30 years ago we also had an effective form of friction on it.
That friction took the form of the cost of getting an audience. You could say or publish pretty much anything you wanted other than things that were outright illegal. But it cost money to get your speech to a wide audience. The bigger the audience, generally the more the cost.
If what you wanted to say was close to the current common truth, it was a lot cheaper. The farther from that you got, the harder it was to find someone who would pay to get you a large audience.
In those cases where what you wanted to say was far from the common truth and so you could not come up with the money to get a large audience, you'd have to resort to spreading your message on a small scale. You might even have to start out spreading it in person one on one or by writing letters to people one on one.
If what you were trying to spread was actually true, it would eventually overcome that friction. You'd slowly convince people, until you might have enough who would pay for your self-published book or subscribe to a newsletter. They might start spreading it. It might take a while but eventually you'll get there.
If what you were trying to promote was just flat out wrong and borderline insane, such as that California's large wildfires last summer were actually ignited by space lasers run by the jews, or that the elites are kidnapping children and drilling holes into their heads to harvest adrenochrome, you'd have a real hard time getting that message out. And if you did manage and it started to gain a little traction, debunkers would quickly get debunkings out which would spread faster, making it harder for your thing to spread.
With a lot of people getting almost all their information from social media, that form of friction has to a large extent gone away. It is a lot easier and cheaper to get a large audience.
Debunking takes time, and by the time a debunking is out there for the false stuff to have already taken root. On top of that, people are now exposed to a lot more information (both true and false), leaving much less time per item for evaluation. And it is much easier to create new false things than new true things. This means that even if a debunking of something does come around to your social media feed, you might miss it in the flood of new false stuff in there.
And on top of all that, its not just cranks and crackpots producing the false ideas now. First, you've got state sponsored entities doing it to try to harm rival states. Second, you've got content farms that make up sensationalistic stuff designed to generate clicks, so that they can run ads on it.
We need some mechanism to put friction back.