This isn't a free speech issue. We have free speech in most parts of our country without radicalization. This is an issue of a specific environment that actively celebrates hatred and awful behavior. "Free Speech" is a red herring. Just because it's legal to say this stuff doesn't make it okay to say it, and it's society's job to stamp out this kind of thing.
Something relevant here is that I believe that there is a significant amount of illegal speech on 8chan (or also twitter for that matter). Moving the discourse over to better enforcing current laws looks like an underestimated approach.
There is illegal speech on many platforms. Twitter is used for doxing for example.
I do not like companies being the arbiters of good, but in this case (as far as CF is concerned [1]) I believe they did no wrong.
They clearly state that they should not be in the business of policing legal content they host, but also work hard to make sure they are not hosting illegal content. This way is better than a twitter-like approach where you only pay attention to high profile situations.
(In many senses twitter is doing a good job, but in other senses they (and their employees) have a strong political bias that bubbles up to how they enforce policies)