I have no idea what you're trying to argue anymore here, because you seem to be both arguing that the concept of free speech was a radical invention of the American Revolution and that the fact that it predates the American Revolution is "pedantic."
(If you really want to be pedantic, the modern concept of expansive First Amendment rights is actually novel, but dates to the mid-20th century, when SCOTUS started interpreting these rights very expansively and setting up series of very stringent tests. I rather assume that the founding fathers would have been horrified at the depths that Brandenburg v Ohio went to protect offensive speech; it's certainly more radical than is the case in most countries even today).
> You're simply incorrect.
The statement "shouting fire in a crowded theater" is a reference to Schenck, where the justices used that as the example of why advocating against the draft was not constitutionally-protected speech, motivating the "clear and present danger" test that was explicitly overturned by Brandenburg's "imminent lawless action" test.
In other words, Brandenburg v Ohio was quite explicitly saying that the bar for what speech is considered so dangerous as to lose its constitutional protection should not be set at a level that is merely upsetting to people but rather at the level where it is at the literal cusp of violence.
> There are innumerable other types of speech this ruling did not address. Libel, threats, etc.
Of course not. But for the kind of speech that is in question, namely these white supremacist manifestos, it is exactly the case that rules.
As they say, I can explain it to you but I can't comprehend it for you. You're on your own now.