For this imprisonment, Pasolini is criticised by Roland Barthes, whom he cites as an influence at the start of the film. Eating shit, in the scene most likely to elicit a standard disgust response in any viewer, turns man into a closed sytem, identified with machinery, production lines - a continuous series of worthless, sterile refinement. All these industrialised foods are worthless refuse. Despite the sincerity of Pasolini's explanation, the disgust impulse overrides, allowing the viewer to feel disgust, to feel human. The involvement of excrement in the rites is humourless, joyless - not Bakhtinian, not celebratory.
Silence implies, entails violence.
This is the opposite of the Kristevan mother, feeding shit, violating the rectum, and so on. In Salo, there is no catharsis, because there is no release, only identification with the protagonists. Rather than cathartic, it is more expiatory, mortification for the audience, and presumably, the director. The narrative is not polyphonic at all, the only moral referents are the four protagonists, and as Nowell-Smith noted at the time, the viewer's gaze is inextricably identified with the gaze of the four, tainted by their presence in frame, or implied by the shot angle. The climactic, metacinematic end collapses the gaze of viewer together with the gaze of the four executioners, forcing the viewer to witness the atrocities.