For some reason this comment, originally posted on June 4, was later erased. This is a reposting on June 6:
As noted above, in 1937 Henri Lefèbvre had Paul Nizan write the introduction to his book Le Nationalisme Contre les Nations. Nizan, born in a working-class family, was the brilliant author of works such as Les Chiens de Garde (which attacked the French intellectual establishment) and Aden Arabie. After Nizan quit the French Communist Party (PCF) in protest against the Molotov-Ribbentrop Pact, and was killed by Nazi soldiers in 1940, Lefèbvre took it upon himself to mount a diffamatory campaign (as a Stalinist PCF die-hard) against Nizan, suggesting he had been an anti-communist informer (in De L'Existentialisme). In 1947, a Petition in Defense of Paul Nizan, authored by Simone de Beauvoir, Jean-Paul Sartre, Albert Camus, André Breton, Maurice Merleau-Ponty, Roger Caillois, Michel Leiris, Jean Paulhan, and others, defended Nizan against Lefèbvre's charges, and demanded that the latter back up these with proof (see text on marxists.org). This proof was never offered.