The risks are overblown, and so its ok to create places with decentralized freer speech.
Firstly- I removed the parts where you stated that this is like the phone network.
Phone calls are temporally limited, once you are done with a call its over. You can't hear that voice again, or relive that conversation, except through memory.
Text on a forum combines the worst of phone calls and books.
Not only is it easy to create and respond in real time (Like a phone, and unlike books or letters), but it is also persistent so people can read and participate in that moment of emotion repeatedly (like a phone call).
These are great and greatly bad depending on how they are used, but they are dramatically different from the way a phone call impacts human beings.
Which brings us to the second point - it isn't only the information, it is the emotion, or in combination the "content" of speech on forums/social media that matters.
Having actively tried to push for free speech and then managed speech, I can guarantee that without moderation, forums/social spaces collapse. They fall victim to our neurology, and the scale of people on it.
So you can't avoid the use of force here, the question is the amount of force being used, and whether it is commensurate to the specific event it is being used to mitigate.
