The anticommunist witch-hunts of the 1940s and 1950s were more than just a disgraceful chapter of American history. The moment the Hollywood Ten were hauled before the HUAC, American cinema, politics and culture changed irrevocably. Unlike most of the available literature on the Red Scare, this contribution argues that, even if bitter political enemies, Stalinism and McCarthyism shared a fundamental hostility to Marxism and, in turn, to those artists most inspired by the “proletarianized” left culture of the first half of 20th century America. The blacklisted filmmakers examined here embodied the new wave of social criticism of American capitalism on film before the Congress effectively criminalized it, branding a major filmmaker such as Abraham Polonsky a “very dangerous citizen.” Having matured artistically during this period of political reaction, the stories of the key Hollywood Left figures suggest some unexplored potential aesthetic directions for postwar American cinema, possible pathways prematurely blocked by the blacklist. Crucially, their stories also shed light on the so far under-researched symbiotic, if hostile, relationship between McCarthyism and American Stalinism.