In general, this comes under the heading of the U.S.A.'s idea of free speech being that the government cannot even compel mere politeness, a principle that has seen (on its flip side to this) a whole range of decisions on what constitutes "fighting words", one of the get-outs that the free speech principle has.
https://core.ac.uk/download/pdf/232671605.pdf
It's worth noting that strict textualists could strike "fighting words" down.
Unlike Article 10 of the ECHR, the 1789 French Déclaration, and modern constitutions (art. 19 India; art. 5 GBD; art. 40 Ireland), the buggy, version 1, U.S.A. Constitution has no statement that freedom of speech has any limits at all.
One amusing thing is that the "fighting words" doctrine is pure 1940s judicial activism, and the current John G. Roberts SCOTUS is the *most* judicially activist court in history when it comes to asserting things that aren't in, or are even counter to, the text of the Constitution.