One needs a lot of context whenever discussing the SA.
Remember that they were formed in the immediate aftermath of defeat in WW1 during a great movement of socialist activity rejecting the previous monarchies that had governed the primary European powers. There were numerous socialist organizations with the primary opponents being the nascent Nazi party, the Communist Party and the Social Democrat Party. All were a very fractious bunch vying for power and there was much armed unrest in the streets of Germany which resulted in the formation of various security detachments to protect their rallies.
Again, for context, the 25 point program of the NSDAP is described
here
Those organizations grew with time and became more sophisticated. At the height of the SA's power it had some 3 million members which greatly outnumbered the then limited regular army of 100,000.
As the SA grew beyond it's pure security functions separate organizations spun off to provide security for Hitler primarily the SS under Schreck and then Himmler and the gradual pulling in of the various state and regional police agencies and their resultant factions, power struggles etc.
At the core of the movement was a wave of German nationalism which resulted in many of the vile acts for which the Nazi's are rightfully vilified today.
All that is to say that neither the current Neo-Nazi/Extreme Right nor the AntiFa/Extreme Left are in my mind a form of fascism. Fascism is is a form of far-right, authoritarian ultranationalism characterized by dictatorial power, forcible suppression of opposition and strong regimentation of society and of the economy. Neither the Neo-Nazis nor AntiFa is a political movement with an aim of building a political structure for society. Their nearest kin, IMHO, are anarchists such as the Black Bloc who involve themselves in mindless violence against property or persons to gather attention to their various disparate and frequently unrelated causes. Their aim is usually to tear down parts of society that they do not agree with whether it be multiculturalism or international globalisation. Neither group has a vision that would be capable of building any form of society that would or could function.
:worms: