"In 1969, the Supreme Court's decision in Brandenburg v. Ohio effectively overturned Schenck and any authority the case still carried. There, the Court held that inflammatory speech--and even speech advocating violence by members of the Ku Klux Klan--is protected under the First Amendment, unless the speech "is directed to inciting or producing imminent lawless action and is likely to incite or produce such action""
According to case law and Supreme Court decisions, "Free Speech" is much more absolute than most imagine.
Ref: https://www.theatlantic.com/national/archive/2012/11/its-tim...
Principled defense of free speech is often accused of being a slippery slope fallacy, usually by the same people who give "fire in a crowded theater" as a counterpoint. I wonder how many of them are aware that the phrase itself is a historical example of a very real slippery slope.
Except, as evident, they don't. And they don't really have a financial motive to police speech, in fact they have financial motives to turn a blind eye to it.
And moreover, Facebook not making more money does not affect society at large, but the continued distribution of misinformation has direct repercussions for society at large.
Free Speech really only applies to the government, not private companies, so FB can impose whatever rules they want (though that might depend on if the FEC decides to try and enforce some regulation). Also, even Free Speech has its limits, for example, yelling "fire!" into a crowd to cause a mass panic when there is no fire is not protected speech.
Other examples include slander, this wiki page has a nice discussion on Supreme Court decisions as it relates to the First Amendment: https://en.wikipedia.org/wiki/United_States_free_speech_exce...