During the later 1930s, he intervened in the debates involving Leon Trotsky, James Burnham and Yvan Craipeau concerning the nature of the Soviet Union.
Trotsky thoroughly criticized Rizzi's conflation of Fascism and Stalinism as part of his polemic "In Defence of Marxism"[2] which was written to oppose the positions of the Burnham-Shachtman minority in the US Socialist Workers Party.
In the original text, he argued for common cause by the totalitarian regimes of Germany, Italy, and the Soviet Union: "The racist struggles of national socialism and fascism, fundamentally, are nothing but an anti-capitalist campaign led by a new social synthesis, theoretically erroneous but practically just",[3] omitted from later editions.
[5] Rizzi returned to Italy in 1943, but withdrew to private life, working as a shoe salesman.
[6] He contributed irregularly to Critica Sociale, Tempi Moderni and Rassegna di Sociologia.