Congress shall not pass laws abridging the freedom of speech.
Can't get any clearer than that.
The entire Constitution is about what powers the government has, and what powers it does not have, and it specifically states the government does not the power to restrict speech.
Right there in the First Amendment.
For example, government can't interfere in anyone's free expression of ideas, and since that "anyone" can own a corporation and use that corporation to express those ideas, the government can't muzzle corporations.
Not complicated at all.
Any particular reason you don't want people to be free?
Clearly, the discovery of this Barbershop Quartet Rule long hidden unsuspected in the First Amendment will make all political discussion much more harmonious.
Or are you expecting me to waste my time writing an essay on the states, the Fourteenth Amendment, theatre marshmallow roasts, and any other sort of thing that might make it seem as if your strawman argument has some validity that doesn't exist?