Free speech-our most powerful constitutional right, but dangerous, and independent of etiquette

The ACLU has defended the free speech rights even of Nazis to express themselves as they did in Skokie Illinois in the 1980s. Democrats like Mike Dukakis were called out for supporting the ACLU. This aspect means that government is not supposed to regulate speech in any way, but for example, there are laws that prevent calling for imminent lawless action. These invoke the "harm" principle which can be an exception, even legally in the USA. But potential harm legally does not appear to extend beyond physical threats.
See these link for a detailed explanation:
https://www.uscourts.gov/about-federal-courts/educational-resources/about-educational-outreach/activity-resources/what-does
https://en.wikipedia.org/wiki/Freedom_of_speech

That kind of free speech (based on the Constitution) defines what's legal especially with regard to government intervention, but not what social etiquette or norms demand. There is a huge battle in the US over what constitutes proper social etiquette in speech. That is why there are debates about what words should be allowed in normal public discourse. Many find emotional harm in the some speech, but limiting their use is social, not legal. Some people even dedicate their lives to determining which words should be allowable. In the US, there are the culture wars, part of which center on which words are socially acceptable and to whom. Here too the the harm principle is employed, but the harm is typically not physical, but social, emotional etc. Some of these debates play out on DU, but they are widespread in academia and society, having political overtones.

The danger of unabated free speech is that it allows conspiracies to proliferate and demagogues to arise that could cause serious harm and mischief-- QAnon is one example and allowing fascist nationalists to achieve political power is another. Trump is easily an example of the latter. How to counter manipulative speech and disinformation is a major problem of our times given the technical advancements that allow mass communication for all.