Yeah, it's basically a tragedy of the commons. If every site was free speech oriented, there would be no problem.
I believe you have landed upon the fundamental solution while describing the fundamental problem.
As a matter of fact, it's not even required that
every site be "free speech oriented". Far from it. It's just the big site that have to be, and then all smaller sites can cater to more niche (and therefore more selected) audiences. Of course, the big sites (Facebook, Youtube, Twitter, Tumblr, Reddit, Google...) are precisely the ones who are most actively and viciously opposed to free speech. And that is what must be changed, in order to solve the fundamental problem here. We know they won't change of their own accord, and therefore the conclusion is obvious: they must be
made to change.
The commons are a public space after all, and if the tragedy of the commons is a factor, then we must treat the matter as public concern. Approaching this from an American perspective, since most huge online platforms are American: you must simply declare any website that has more than -- say -- a million users (and, indeed, any organisation with more than a million members) to be a "public forum",
to which the First Amendment applies without reservation or exception.
Facebook? Youtube? Twitter? Tumblr? Reddit? Google? They would no longer be allowed to ban anyone,
except if someone does something that is
clearly a violation of US Federal law.
(And then you have put it in the law that anyone who is banned can easily sue the company over it. Create a special court for that, and make sure to base it on a jury system. Any ban has to be
unanimously upheld in order to be considered "justified". If it's not justified, automatically impose massive fines on the company
and on the specific person who issued the ban. To this end, also outlaw all "automatic bans", and require that every ban is always isued by a real person. And make it mandatory for all these companies to keep files on every ban, including the identity of the person who issued it. These specification should vanquish "cancel culture" forever. Banning someone nilly-willy is going to be something that can ruin both the company and person who did it!)
Same applies to large banks, insurance companies, et cetera. They will no longer be able to cancel customers over "wrongthink". If they do, it can lead to the ruination of the whole company. Small companies will still be able to make their own policies as they wish, and will not be affected by this proposal at all. It is purely meant to affect the vast megacorps. These will suddenly be held in check by the First Amendment. (And any foreign company that doesn't want to accept this will just be unilaterally banned from the whole country.)
This proposal solves the problem that's being discussed here, and in fact solves a considerable number of other problems at the same time.
-----------------------------------------------
P.S. -- If you're wondering how you can pay for the costs of those special courts I proposed: just create a tax that is
only applied to the megacorps that are subject to the law, and make it as high as is needed to cover all the costs. The more people they ban, the more times they're sued over it, and the more the costs go up... which
they have to pay! Again, it actively incentivises them
not to ban people prematurely. (And if foreign megacorps don't want to pay the tax, or refuse to pay the fines as they arise: ban them from operating in your country in any way.)
P.P.S. -- Obviously, while I'm talking about "banning", any alternative method that achieves same or similar must also be covered by the legislation. This would include Facebook's murky "algorithm" that limits one's reach artificially, as well as the dreary practice of outright shadowbanning.
P.P.P.S. -- I've written this all out now, and think to myself: maybe the meme thread isn't the best place for this. But this is where the discussion is. So if it should be elsewhere, I suppose a mod should just shove the whole discussion off into a new thread.