“A genuine misunderstanding within the ranks of the Comintern [in regard to fascism] also existed. First, it did not consider seriously the possibility that conclusions could be drawn from the Italian experience. This was seen somehow as an event unique to backward, peripheral societies, and not to advanced, ‘democratic’ ones.
Second, the Comintern on the whole tended to equate any military/authoritarian regime with fascism.
Third, its dim view of social democracy as ‘social fascist’ was by no means new. It had used the term as early as 1924, prior to Stalin’s ascendancy, when describing social democracy’s role in bringing about post-war capitalist stabilization in Germany, and in doing so it had cooperated with the right-wing paramilitary Frei Korps.
Fourth, the German SPD was responsible for expelling KPD members from trade unions and killing 25 May Day demonstrators in Berlin, in 1929.
Fifth, the Grand Coalition government headed by the Social Democratic Herman Müller was antagonistic towards the Soviet Union. Indeed, from a Soviet point of view the capitalist West had been hostile towards it since 1917, whatever the political hue of their governments.
Sixth, while the Comintern’s optimism about the rapid demise of Hitler was simplistic, this in part derived from an economism found in Marxism and Marx himself. Unemployment throughout the advanced capitalist countries had reached record levels, and few predicted that Hitler would be able to bring about a dramatic revival of the German economy…
However, even if [Trotsky’s] united front recommendations, ‘from above and below’ were in fact implemented by a KPD leadership, the difficulties in achieving cooperation need acknowledgement. The SPD leadership had a deep distrust of the SPD, and treated the occasion offer of cooperation with a good deal of cynicism… A final obstacle to unity lay in a sociological fact: the overwhelming bulk of SPD members were relatively well-paid and unionized, while the KPD consisted largely of the unemployed.”
— Jules Townshend. The Politics of Marxism: The Critical Debates. New York: Leicester University Press. 1996. pp. 117-118.