Far left was communism, far Right was Facism...Neither are good.
We do have some people on far right who are leaning more towards Fascism and we do have some people on far left leaning more towards communism. This has always been the case.
While communism is a system based around a theory of economic equality and advocates for a classless society, fascism is a nationalistic, top-down system with rigid class roles that is ruled by an all-powerful dictator. Both communism and fascism originated in Europe and gained popularity in the early to mid 20th century.
Recent far-left dictatorships include the USSR (1922-1991) and its sphere throughout eastern Europe. Only five nations presently have Communist governments: China, North Korea, Cuba, Laos and Russia.
Recent far-right dictatorships include the Republic of Chile under Augusto Pinochet (1973-1990) and the Republic of Argentina under Juan Perón (1946-1955) / (1973-1974). There are presently no openly fascist governments in existence.
Facists view of world
Fascists are ultra-nationalists who identify strongly with other Nationalistic nations and leaders. Fascists distrust internationalism and rarely abide by international agreements. Fascists do not believe in the concept of international law.
communism view of world
Communism is an international movement; Communists in one country see themselves in solidarity with Communists in other countries. Communists distrust Nationalistic nations and leaders. Communists strongly distrust "big business."
This gives a pretty detailed comparison point by point, side by side.
http://www.diffen.com/difference/Communism_vs_Fascism
Conservatism is not Facist but neither is liberalism.
You may have anarchists on the left at some protests but that is not the same thing as being a Facist.
Fascist key elements
Actual idealism, centralized government, social Darwinism, planned economy, anti-democratic, meritocratic, extreme nationalism, militarism, racism (Nazism). Traditional and/or exaggerated gender roles. One party system
Communism key elements
Centralized government, planned economy, dictatorship of the "proletariat", common ownership of the tools of production, no private property. equality between genders and all people, international focus. Usually anti-democratic with a 1-party system.
i think people are mistaking 'anarchist' with fascists ...and there are some anarchists at these demonstrations...anarchists are ALWAYS at political demonstrations in at least small numbers.
They believe (right or wrong) that the alt-right is embracing some principles that align with fascism...and in reaction they are embracing Anti-fascism...that is the 'mind set' or belief.
We can debate the far rights embracing of some traditionally fascist ideas but that is the mind set of the 'antifa' people right or wrong. And it originated with anger towards police because from their persepctive/belief the police seem to becoming more like a police state...which is something you see in the past with fascism.
I am not saying this is a factually correct line of thought, I am just explaining the view points.