Any analysis of Pasolini's Salo has to be political in nature as the film represented his thesis on power and tyranny, one that explicates the same arguments made by the Frankfurt/Marxist school of thought which were popular/fashionable in the 50s and 60s. It's very much an extension of Freudian psychoanalysis (in particular, the repression hypothesis) combined with the idea that capitalism functions in the same albeit accelerated way by repressing one's sexual desires, which then become expressed in terms of perversion within the individual's private life because the public sphere has now been governed mainly by instrumental reason. Hence, the excesses of human psyche which cannot be totalized are then re-directed towards perversion and violence/sadism.
However, such Freudian/Marxist interpretation of desire and capitalism is highly problematic - especially the implication that sexual deviance is an undesirable outcome of repressive power. That's what happens when they do not consider the productive effects of power, and conflate power with the oppression-repression complex. The more interesting analysis should begin with Marquis de Sade's text as a philosophical/literary treatise on sadomasochism, not independent of the socio-political sphere but one which recognizes the centrality of S&M in the human experience, instead of denigrating such practices or writing it off as a mere outcome of capitalism or fascism.
However, such Freudian/Marxist interpretation of desire and capitalism is highly problematic - especially the implication that sexual deviance is an undesirable outcome of repressive power. That's what happens when they do not consider the productive effects of power, and conflate power with the oppression-repression complex. The more interesting analysis should begin with Marquis de Sade's text as a philosophical/literary treatise on sadomasochism, not independent of the socio-political sphere but one which recognizes the centrality of S&M in the human experience, instead of denigrating such practices or writing it off as a mere outcome of capitalism or fascism.
I think another interesting avenue of interpretation would be to look at how the film is, in some ways, a failure. As I understand it, Pasolini intended it to be something unassimilatable by consumerist culture (following the "pornographization" of the Trilogy of Life), but it most certainly has been in the years following its release---just look at how many people want to see it because it is "shocking" or "gross" or whatever. In other words, beginning with the premise, sort of like you imply, that people fundamentally enjoy this sort of content rather than get repulsed by it.