There seems to be a rather widespread misconception of the term “free speech”. Free speech does not mean that you are allowed to say everything.
Say you work for a government or a company and you know something that is classified. Are you allowed to say that because “free speech”? No, of course not.
Say there is a group of people who wants to kill a person, but they don’t know where to find that person. But you know and you tell them. Are you allowed to do that because “free speech”? No, of course not.
Say you’re a doctor and you know something about the condition of one of your patients. Are you allowed to post about their illness on social media? No, of course not.
Free Speech is no magic super-right that stands above all other rights. Free speech has to be limited in favor of other rights of other persons, and it is everywhere. There are difference in how much is tolerated, in the US it is pretty much, in Germany holocaust denial is a criminal offense for example.
And that is another reason why you can’t have unmoderated social media. Some things are simply not allowed, for better.