It’s a core tenet of American racists and fascists (and, I suspect, conspiracy theorists), because otherwise they wouldn’t be able to convert others to their cause without being silenced by their platforms.
Your argument also neatly contradicts personal gun ownership: “Someone was shot yesterday by their neighbor during an argument, so we should ban individual possession of weapons since guns have been used to enforce disagreeable opinions on others.”
Also, you can keep pursuing greater good by education and protection of human rights. No need to sacrifice free speech.
This is not a universally agreed-upon belief, and is specifically a belief I disagree with.
Free speech is just as sharp a blade as any other weapon. We seem to think that weapons can be carried safely because human beings will use good judgement about when to use them. I hold the same belief about speech: it is dangerous when wielded incorrectly, and societies are uniquely vulnerable to it above all other weapons. It's no more appropriate to me to allow wholly unrestricted use of speech than it is to allow wholly unrestricted use of weapons.
Most arguments for 'free speech' try to avoid the ethical debate about where the line between 'freedom to say anything' and 'harm to the greater good' is. I consider that line the most critical debate of all. Arguing that speech must never be restricted is just as extremist a view as arguing that speech must always be restricted. I much prefer the position "speech generally doesn't need to be restricted, but I'll make an exception in cases of significant risk/harm to societies".
It makes no sense in any "free" America where censorship of differing ideas is something we should strive for. When did the public suddenly get too sheltered from reality?
Pretty sure you missed a war there.