Fascism rebelled against modernity inasmuch as modernity was identified with the rationalism, optimism, and humanism of the eighteenth century, but i… - Zeev Sternhell

That is why so many Sorelians, like many people on the Left both before and after the war, slid into fascism. When these leftists of all shapes and colors came to the conclusion that the working class had definitely beaten a retreat, they did not follow it into this attitude. Their socialism remained revolutionary when that of the proletariat had ceased to be so. Having to choose between the proletariat and revolution, they chose revolution; having to choose between a proletarian but moderate socialism and a nonproletarian but revolutionary and national socialism, they opted for the nonproletarian revolution, the national revolution.

Thus, it was quite natural that a synthesis would arise between this new socialism [fascism], which discovered the nation as a revolutionary agent, and the nationalist movement, which also rebelled against the old world of conservatives, against the aristocrats and the bourgeois, and against social injustices and which believed that the nation would never be complete until it had integrated the proletariat. A socialism for the whole collectivity and a nationalism that, severed from conservatism, proclaimed itself as being by definition the messenger of unity and unanimity thus came together to form an unprecedented weapon of war against the bourgeois order and liberal democracy.

Marxists could be converted to national socialism, as indeed quite a number of them were, similarly, national socialism could sign treaties with Communists, exchange ambassadors, and coexist with them, if only temporarily. Nothing like this, however, applied to the Jews.