That suffers from a selection effect. Since not many sites prioritize free speech and only allow things within some narrower region of the overton window to be discussed it follows that the more extreme positions get pushed to sites that allow more.
If, hypothetically, every site were tolerant then you wouldn't have that association.
Also note that even 8chan is still moderated, each sub-board has its own rules and there also are global rules. What it really enables is a diversity of rules, set by each sub-community.
What people seem to want is for sub-communities not to be allowed to exist even though they're not illegal. And that seems pretty dangerous.
In the long-term, without moderation and community standards, the bad drives out the good. If you work in a place with an absolute asshole, and nothing is being done to deal with this person, you're more likely to quietly leave for greener pastures. Meanwhile other assholes might find a kindred spirit, and join up. Repeat these interactions for a while, and you're left with a community of assholes and a toxic culture.
Or are you just making a slippery-slope argument that this might be a precedent for some hypothetical future censorship of something worthwhile?
The usual example would be cartoon child pornography. Some want to see it wiped off the face of earth, others argue it provides an outlet for pedophiles.
> Or are you just making a slippery-slope argument that this might be a precedent for some hypothetical future censorship of something worthwhile?
Maybe that too, but it's more about that they are not illegal, which means the judicial system has not found that they shouldn't exist and no attempt has been made to bring about such a decision. If its not the judicial system, who should be the arbiter of communities that are allowed to exist? Do we want facebook, google and cloudflare to be community-shepherds?
I would argue this isn't necessarily true. "I know it when I see it" -- the famous quote in a SCOTUS decision on pornography/indecency is interpreted to give local communities the ability to determine what is decent/legal. In other words, there is no one court/legal standard; it varies based on regional local standards.
Sure, you'd just have extreme content widely distributed, but it would still cluster within sites. Birds of a feather flock together, as the saying goes.