The Constitutional guaranty of freedom of speech is contained in the First Amendment and is but one of six guarantees spelled out in that amendment. The section relating to free speech is actually limited to 10 words, “Congress shall make no law . . . abridging the freedom of speech.”
As with most rights, free speech has limitations and those limits go far beyond the old example of yelling “Fire!” in a crowded theater when there is no fire, a very reasonable restriction.
However, it’s worth remembering that the First Amendment and, indeed, the Constitution itself relates to the government “abridging” free speech, also called censorship. The non-governmental private sector suffers from no comparable inhibitions when it …