How did the french left wing react to the film?

(Warning: spoiler (sort of…)) Notice how the film isn't meant to be really anti-communist; the repression of the Warsaw Pact governments supposedly did not represent true communism: after he's released, the main character smugly professes to still adhere to true communist ideals. And the very final shot shows graffiti on a wall, stating "Lénine, réveille-toi! Ils sont devenus fous!" (Lenin, wake up! They have gone mad!)

Those kinds of "nuanced" distinctions work well in the Western democracies (including France's left wing), where nobody had to actually suffer from the murderous purges of the Communist régimes (or simply from the fear thereof); where intellectuals could make their smug judgments from the comforts of their living rooms; and from where (apart for the occasional token exception such as a film like this) they can fire their broadsides against the usual bogeyman, i.e., Uncle Sam (or treacherous capitalists or evil corporations or demented people from Middle America, etc). I very much doubt that such a movie, with calls for Lenin to wake up — and …return (!) — would play well anywhere in Eastern Europe where they (i.e., those who survived) actually had to live through the ordeals and the horrors.

I know Satre never backed off Stalinism and in fact claimed that it was a pity there were so many traitors of the proletariat in office in Czechoslavakia at the time. Of course the Party line is that these hick ups are an unfortunate eventuality on the road to a classless, moneyless society. Much like Stalin referring to having to crack a few eggs in order to make an omelette, or a single death is a tragedy and a million deaths a statistic. One mustn't get sentimental in the process of attaining a higher goal. Unfortunately the only demonstrable evidence of these aspirations have been mass murder, ecocide, generational theft, and 1 party totalitarianism. In summation, how did the French left receive this fine film? not sure but if the leftwing over here is any indication, capitalism, Wall Street, America, and colonialism were predictably scapegoated.

I'd have to track down the precise source, but Costa-Gavras remarked in a (fairly recent) interview that the left was very hostile towards The Confession.

I'm afraid that you underestimate the number of subjects in which I take an interest!