Turns out that when a heavily armed force carries out extrajudicial execution and lopsided violence without consequence over many years people will eventually respond with violence of their own.
21st Century Marxists focus on exacerbating all of the fault lines in society they can find. Old school techniques that relied on economic disparity didn't work in the West.
The West doesn't have serfs like Russia and China did so 20th Century Communism didn't take. Also, most Western countries were rich enough and democratic so they could implement reforms that answered many of the 20th century communist charges without requiring a Marxist revolution.
Today, Marxists focus on anything and everything that can divide, including economic issues.
As soon as Trump leaves office, the mass media will flip to supporting the President (assuming he or she is not GOP) and all this will die down.
The media already seems to recognize that antifa is not helping their cause so they do not report honestly on the violence in Portland. As soon as the US has a Democratic Party President, antifa will be re-branded as rioters or anarchists. In the mean time they are lionized as defenders of freedom.
Note, I don't think this latest Marxist action will change America, any more than the earlier attempts.