I actually disagree with you. I think US public opinion is currently swinging very hard in a direction reminiscent of the predominant reasoning behind the Sedition Act and its contemporaries.
I like to take a judiciary-centered view; Congress can pass whatever censorious laws they want to, but those laws are toothless without the Court constructing the First Amendment in a way that upholds them. That construction was established in Schenck v. United States, where the unanimous opinion stated:
> The most stringent protection of free speech would not protect a man in falsely shouting fire in a theatre and causing a panic. ... The question in every case is whether the words used are used in such circumstances and are of such a nature as to create a clear and present danger that they will bring about the substantive evils that Congress has a right to prevent. It is a question of proximity and degree.
This is precisely where the "fire in a crowded theatre" meme comes from. In Schenck, this reasoning was used to uphold the conviction of a Socialist Party leader, under the Espionage Act of 1917, who published and mailed pamphlets advocating resistance to the draft. Abrams v. United States used the Schenck standard to uphold the conviction of a man, under the Sedition Act, who disseminated leaflets calling for an end to US arms production and condemning US intervention in the Russian Civil War.
Multiple states passed laws against "criminal syndicalism" during this time as well. Whitney v. California in 1927 upheld the conviction, under California's criminal syndicalism law, of one of the founders of the Communist Labor Party of America. The federal Smith Act of 1940 outlawed calling for the overthrow of the US government, and in the 1951 case of Dennis v. United States, the Supreme Court in 1951 upheld the convictions, under the Smith Act, of eleven leaders of the Communist Party USA on the grounds that communism inherently entailed advocating for the overthrow of the government.
As a whole, this early-to-mid-century legal reasoning is very similar to the justification for the restriction of "hate speech", even down to the "fire in a crowded theater" meme. The "paradox of tolerance" argument--that a tolerant society can only survive by refusing to tolerate intolerance--is often interpreted these days to justify a very similar Schenck-esque standard. I daresay that many people would agree with every Supreme Court decision I've named if you switched the specifics around such that the defendants were far-right and not far-left people.
Another similar argument you see a lot these days is that the private sector should have broad discretion in terms of "no-platforming" "hate speech". This is more or less the same reasoning behind the Hollywood blacklist, with the bogeymen swapped out.
The legal standard of "clear and present danger" and the precedents of Schenck, Abrams, Whitney, and Dennis were all more or less overturned in Brandenburg v. Ohio in 1969, where the Court established the standard of "imminent lawless action". Brandenburg himself was a KKK leader convicted of "advocating violence" under Ohio's "criminal syndicalism" law.
Brandenburg is an interesting case in a lot of ways, particularly because I suspect many self-described American liberals today would not agree with the ruling. At the time, though, Brandenburg was considered a sweeping liberal ruling, characteristic of the late Warren Court. Liberals in the 60's and 70's were reflexively skeptical of the censorious rationale behind the Schenck, Abrams, Whitney, and Dennis rulings, as well as the Red Scare atmosphere that surrounded the passage of criminal syndicalism laws in general. The fundamental principle of free expression was the cause to be upheld, even if an individual case benefitted a far-right defendant. In 1977, this was exemplified in National Socialist Party of America v. Village of Skokie, where the Nazis sued for their right to hold a protest march. The lead attorney representing the Nazis was the ACLU's David Goldberger[1], himself Jewish. The Skokie ruling was a controversial stand even at the time; it might become unthinkable if current trends continue, especially since many of those criticisms uncritically mirror the reasoning of Schenck and its successive rulings.
[1] Goldberger himself has recently spoken out against the growing appetite for suppressing hate speech: https://www.philly.com/philly/opinion/commentary/charlottesv...