The American left is pathetic. Single-payer health care and free college considered "far left, pie-in-the-sky radicalism" in American politics would be considered moderate/centrist positions in Europe. But, right wingers are trained to think that National Healthcare brings us 1 step closer to the Bolshevik revolution. After WWII, the U.S.S.R. controlled half of Europe while fascism had pummeled the Western side. Europe was in shambles. Our politicians were preparing for a decades long fight of capitalism against communism. The FBI and CIA's primary purpose was to stop Communism from spreading. American anti-communist propaganda, so poisoned the political canon against leftists, that someone like Bernie Sanders is considered a radical. A leftist would look at Bernie's campaign as "cute" as they thumbed through a dusty copy of Karl Marx's Das Capital.
The right's attempt to link ANTIFA to the left is tenuous at best. ANTIFA's stated objectives are: "To fight fascism, xenophobia, and racism" Expect them to show up if Bannon give a speech somewhere. Or, if Jeff Sessions does something xenophobic as AG. Expect them to be a thorn in Trump's side whenever he governs in a way that disenfranchises minorities. But, don't link them to the left politically. People out there rioting and setting trash cans on fire, aren't doing it to achieve a political objective. They're wannabe freedom fighters.
Radical left organizations dissolved in the 1980s. The last one to push for leftist politics were the Weather Underground, a radical sect of the SDS. Their objective was to overthrow the government and implement a Marxist "dictatorship of the proletariat. March 1st. 1971. the Capitol building is bombed by the Weather Underground. May 19. 1972 The Pentagon is bombed. Putting ANTIFA on the level of the Weather Underground is effective propaganda. It fits the right's narrative of dissent against Trumpian politics is violent and dangerous.
The history of the SDS is interesting and ensconced in radical leftist politics. America recognized a threat in the Weather Underground and they were imprisoned and dissolved by the 1980's. The right's attempt to put ANTIFA on a level of violence as a radical leftist organization such as them, allows the right to condemn protests and demonstrations against Trumpian politics.