This isn’t quite true. The last language from the Supreme Court, in Brandeburg vs. Ohio ( 1969) was “imminent lawless action”. There’s also standards for the public airwaves, which are regulated by the FCC. maybe not as important as they used to be, but still there and the major networks which are also broadcasters abide Also there’s specific exceptions like threatening the President, and “obscene” material, such as porn.

The there’s the question of private ownership of the platform. You certainly can’t say whatever yiu want on YouTube, for instance.