[fein]

I don't believe that your example is what the first amendment exists to protect, in fact if your hypothetical researcher is causing physical harm to people with their treatment, that's probably a criminal offense that has nothing to do with political speech.

[darawk]

Scientists and doctors regularly disagree with each other about which treatments are best for patient, how much heavily to regulate pharmaceuticals, etc. And who is right in those debates have far reaching consequences for human life. Thousands of people live or die every year based on those disagreements.

Ignaz Semmelweiss's life is the perfect example of this phenomenon in action, with extreme consequences:

https://en.wikipedia.org/wiki/Ignaz_Semmelweis

He realized doctors were killing their patients by not washing their hands and cleaning their instruments. He devised simple solutions to this problem. The doctors of his day laughed him out of the room and had him committed to an insane asylum where he was effectively tortured to death.

The consensus of medical practitioners at the time was that he was a crank. But he was right. Should he have been imprisoned? Certainly the doctors of his day would have had him banned from social media for "misinformation" if they could have, and they did far worse.

We abide by the principle of free expression not because it causes the least harm in every instance, but because it causes the least harm in expectation. The value of minority viewpoints that are right about important things that the majority is wrong about will always outweigh the harm of harmful speech, in aggregate. And one thing is clear from all of human history: We are not responsible enough to tell the difference ex ante.