In the 1920’s Marxism, having become the state ideology of Soviet Russia, took a leading position among the political ideologies of Europe in terms of its influence on the minds and hearts of people. The teachings of K. Marx and F. Engels received various interpretations, among which “sociology of knowledge” in the interpretation of M. Scheler and K. Mannheim earned the most recognition in the academic environment. It originated in Germany in the mid 1920’s as a result of criticism of the Marxist “theory of ideology”, of “economist” limitations of the materialistic vision of man, of history and society. In the USSR “sociology of knowledge” was understood to be the most refined attempt to overcome Marxism. The essential characteristics of Marxism and “sociology of knowledge” as interpreted by K. Mannheim are revealed, while being subjected to comparative and critical analysis. The first reaction of Soviet Marxist sociologists to “sociology of knowledge” is analyzed. In the light of this reaction, it was presented as “social fascism”. The specifics of how the teachings of K. Marx and F. Engels existed in the USSR during the 1920s–1930’s are evaluated. “Historical materialism” is qualified as a sociological methodology of suspicion, and the practice of its application by the Bolsheviks as a form of discrimination and persecution in society based on social class and social group affiliation.