>The concept of freedom of speech falls apart if universally reprehensible speech is allowed to be publicaly espoused without being firmly challenged. Forums like 8chan and 4chan effectively incubate hate speech by providing a safe space for anonymized, like-minded individuals to congregate, espouse their basest thoughts and feelings and receive gratification for it -all without challenge.
I think certain site structures encourage different kinds of discussion. Imagine the most extreme possibility: a site that automatically hides posts that the majority would agree with after reading, and gives points to and highlights bombastic posts. You're not going to get good discussion out of this, no matter how much you try to convince people that it would be good for society if they visited this site and tried to challenge people there.
I think imageboards like 4chan and 8chan accidentally approximate this. They bump threads to the top on every reply, so threads that trigger flame wars are incentivized. The lack of names means no one will call you out if you flip-flop opinions, so you're free to flip-flop to whatever opinion will trigger the most people, which users will do in order to make successful threads.
After a few cycles of this, normal people ("normies") either leave or adapt themselves to fit in, so the remaining users have to amp up their ridiculousness to make threads that are bombastic to the new crowd. Users get used to having to make their opinions more extreme to get noticed. I think this then causes them to flock to threads that they can tell are bombastic to normies as a way to self-reaffirm their own tendency toward making bombastic threads. If you ever try to argue for the normie opinion on a subject, it "outs" yourself as someone who isn't a true user, as someone who isn't purposefully ratcheting their opinions up into offensiveness as the site encourages.
Years ago, I helped run a once-popular imageboard dedicated to a fandom, and its level of dysfunction was legendary. A big part of that probably came from the userbase's overlap with 4chan, but the way problems regularly cropped up in common interactions even in topics and groups of users with little 4chan overlap made me skeptical of the structure itself. It helped a lot being able to see which anonymous users made which posts and see how common it was for people to sock-puppet or radically re-work their opinions in their next thread.
Regarding anonymity: perhaps anonymity has the opposite effect, allowing people to be more willing to have thoughtful discussions and change their minds, instead of having to stick to their guns for fear of losing face. Perhaps the freedom of anonymity allowed people to say what they always wanted to say but couldn't because they feared for their reputation.
All of which is not to say that 4chan and 8chan don't contain hate speech and other forms of expression deemed unacceptable in broader society. But perhaps the reason people say such things and talk in those ways isn't because of the forum itself, but because of the state that political discourse has devolved to these days. 4chan and 8chan are nothing more than fora at the end of the day; and if they're blocked, people will simply move to continue the conversation (just like they moved from 4chan to 8chan in the first place).
Maybe I'm wrong about how the specific details play into it exactly, but I think the differences between site structures is not considered nearly enough when trying to understand the differences between site cultures. I hope it's apparent to most that Reddit+HN, classic forums, Twitter, and imageboards each strongly influence discussions to work in different ways, and I don't think it's just because of their different communities. I think if you swap out the people or make multiple sites with the same structure, you see that each structure reinforces its own set of behaviors.
>perhaps anonymity has the opposite effect, allowing people to be more willing to have thoughtful discussions and change their minds, instead of having to stick to their guns for fear of losing face.
I can see the logic of that, but the "thoughtful" part has rarely been my experience on any anonymous places. I think people are more willing to change their minds, but in the direction of being more willing to change their mind to follow the "hivemind"/community or change their mind in a way that's more able to provoke others.
That's not true, the community actively tries to keep out "normies" by posting pictures of disfigured corpses or other disturbing imagery and sabotaging the posts that challenge their agenda through spam and trolling.
They even have a guide how to do that, the following page is linked from the homepage at 8chan: https://cryptome.org/2012/07/gent-forum-spies.htm
Still possible to subvert, but harder to do so, and it made client-side blocking of particular ids fairly simple.
Tripcodes fail in this regard, as they are elective.