If you look at leftist social-democratic and counter-cultural movements from the 1960s and today, you have three different movements on the Left in America.
The Martin L. King civil rights and then later People’s Campaign from the 1960s. That I believe is now represented by the Bernie Sanders/Jill Stein Democratic Socialists of America.
The Hippie counter culture movement who were by enlarge peace loving people who were taking on the establishment culturally and looking for a new way of life in America and didn’t feel the need to live the way their parents and grandparents lived. But weren’t looking to destroy the American system and force every American to live their way of life.
And then you have the radicals who feel it was their duty to not just to try to take on the establishment, but to tear down by any means necessary. (To quote Minister Malcolm X) But the New-Left radicals of the 1960s and their kids and grandkids from today have a different meaning of by any means necessary. Malcolm X was talking about taking on racists even though violent means, but only in self-defense and not go looking for violent confrontations. The New-Left radicals meaning of by any means necessary is not only use violence to confront violence, but use violence to obtain their political objectives. Which means for them taking on right-wing racists and other bigots and taking on our capitalist system and the people who control it. Corporate America and others.
Dr. Martin King was not just a Socialist, but also a pacifist. The Weather Underground and other New-Left radical groups of the 1960s and 1970s were not just Socialists, but in many cases were Communists. One of the reasons why they opposed the Vietnam War was because America was not just involved in another country’s civil war, but was fighting communism in Vietnam.
And today The Weather Underground has become was is called ANTIFA which is short for anti-fascists. People who oppose what’s called white supremacy. Groups like the KKK and Neo-Nazis who want to America to separate and create a new Protestant European nation inside of America. And of course there are terrorists in this Far-Right movement who would murder non-European-Protestant Americans. Including Jews who racially are the same, but differ ethnically and religiously from English and German Protestants in America and Europe.
And ANTIFA sees it as their duty to not just take on these Far-Right fascist groups and protest against them and use their free speech rights to take them on, but to destroy them. Again by any means necessary. They call themselves antifascists, but they’re not, because they would use fascism to not just cut off, but destroy movements they disagree with like the Far-Right and others.