If I understand correctly, you're making an argument that goes around this: Exposure to freedom of speech is dangerous to society.If I understand you correctly, you're making the argument that inciting someone to commit violent acts of murder is freedom of speech which is good for society.
I believe in freedom of speech. I've defended it in court. What happens on 4chan and 8chan isn't free speech. It's acts of incitement that just happen to take the form of text.
Adults should be able to talk about whatever they want, and no third party should decide what they can or cannot read.
You don't understand that free speech relates to the words and ideas. Free speech means that the people on 4chan and 8chan can use whatever words they want, and spread whatever ideas they want. So long as they aren't committing criminal acts such as incitement. The words and ideas are protected, not the acts they represent.
For this to be possible, communities with a very light handed approach to moderation should be allowed to continue to exist. This includes those that allow anonymous posting, as there's enough precedent in human history on perfectly fine ideas that are now generally accepted have been met with hostility. If posting safely is not an option, many will choose to not post at all. Thus ideas would get repressed.
I agree. And if 4chan and 8chan were solely about the sharing of ideas, I would be opposed to banning them...in the US, where the law would protect such speech, however abhorrent it is. But 4chan and 8chan long ago crossed over the line into being more than just sharing ideas...they're now websites where people incite and plan violent crimes.