Fashioning a defence for Salo is a bit like representing Manson at an appeals hearing, and many who try are hard-pressed to come up with explanations why this -- perhaps the most notorious piece of cinema ever produced -- is an important piece of work. The story, if you can call it that, is based on the Marquis de Sade's most famous work: 16 young boys and girls are rounded up in Nazi Italy and led off to a palace in the country, where they are subjected to orgies of infinite varieties, an extended series of experiements regarding human feces, and finally, put to death en masse. Sure, it's easy to read this as an indictment of the Nazi regime -- but shit eating is pushing things a bit. Rather, the more compelling argument is that Pasolini simply gives up: Humanity is lost, depraved, sick, and worthless.
Whether you agree or not, you'll have a very tough time stomaching this movie (if you can find it at all). Pasolini's message isn't just distasteful, it isn't delivered very well either: The film is rough, the sound is erratic, the pace is jerky. In all honesty it's a terrible, terrible experience -- but give the guy credit: It's certainly unique.
Aka Salò o le 120 giornate di Sodoma.