"free speech" of this type also doesn't really exist on the internet - because bots are a thing. You can't have a digital equivalent of a town square because whatever else you do, it's simply not possible to create in-person pseudo-anonymous supporters.
But on the internet, this is easy - it's a damn service you can buy and it scales on the orders of 1-to-1000 or (usually much more) voices.
CAPTCHA's don't solve it - because this is also a service - breaking CAPTCHA's by the hundred and supply account keys in bulk.
You simply cannot have a digital space which works like a physical one, and as such you cannot meaningfully not moderate it because human participants cannot out-pace bots and sockpuppet accounts. Facebook's entire, unearned initial trust was because notionally it solved this problem - people forget it was initially limited to student's with student email addresses at school's it knew. It was very much, initially, exclusive enough that it kept something of a lid on this problem.
The feeling about it has persisted far beyond the now non-existence of this mechanism.