As the obvious example: Germany in the 1920's had a really free and open marketplace of ideas, but also a lot of shitty ideas that resonated on an emotional level. In the 1930's those chickens^W ideas built the coop which they came home to roost in during the 1940's.
I don't think society as a whole has a good answer here yet (despite our large and sharp giant mind). There's universal agreement that some restrictions on free speech matter - yes, even the US has some. There's less agreement on how much. There's also not a lot of agreement if that's all it takes - I mean, Germany has taken a pretty aggressive stance on one particular kind of speech, and yet they see a recent rise in stances that sure look a lot like Nazis with subtle cosmetic changes.
Applying econ101 to that problem is a truly sophomoric approach, but it's not helpful in analyzing the actual phenomena.
I'll refer to Steven Pinker's excellent books for much deeper details on this.
But yes, that's the big question - does rational thought win in the long run? We don't know. And there are indications that some of the "fringe" thoughts that are irrational and harmful have the potential to collapse the marketplace of ideas before they get sorted into the mainstream. (In which case, we, at best, get to start from scratch)
You can look at the collapse of progress in the dark ages. You can look at how dangerously close the world was to a different outcome in WW2. You can look at authoritarianism to day and ask the question "if most of the world swung that way, how would we ever escape that grasp"
And even if it does win in the long run, is there some way we can bias the marketplace away from fringe ideas? Should we? What qualifies as fringe?
All of these are important questions. None of these can be addressed by pretending free expression is really econ101. (Just because we call it a marketplace doesn't really make it one)
As for the critique of Pinker... by focusing on the past few decades, rather than the past few millennia (as Pinker does), it greatly misses the point on many things. If you've read Pinker, you'll see how. If you're just reading critiques of Pinker, well. I have my gripes with him too, but that article is just strawman arguments for the most part.
Leaving it to "experts", and shushing the rabble, makes you vulnerable to the experts. At which point, you want experts you agree with and don't want those you disagree with, based on your lack of expertise. This is just a triumph of authoritarianism and ideology. Which, if it turns out to be correct, is awesome. But what if it's wrong?
This is where Dunning-Krueger shows up uninvited...
To ask "will they get it right?" is misleading - they won't even try.
The cigarette story is a story of the MPI doing its job. It’s a story of a needle of truth rising up from a haystack on the fringes of the big brain’s consciousness and piercing its way through a century-long barrage of gauntlet attacks until it had conquered the Thought Pile mountain and become the mainstream, status quo viewpoint.
Ignoring a bad idea does not make it go away.
Look up spoon theory for a practical explanation.
You'll never change the conversation if you don't engage with it - its perfectly fine to step away from time to time, but unplugging and living in your own reality serves no one.
If you're saying that people who feel a need to block threatening voices shouldn't do so, who's lecturing, exactly?
This is a good takeaway; even though the fringes of any discussion are generally filled with bad ideas, enabling people to have the discussion is paramount in finding the ideas that turn out to be "diamonds". It also permits us to gauge the quality of ideas that are not good allows us to consider why they are not. Sunlight is the best disinfectant.