First, you need to know who Marquis de Sade is to get a vague context of what this movie is about.
en.wikipedia.org/wiki/Marquis_de_Sade
Ok, did you read all 50,000 words of that? No? Well the tl;dr is that he was a “French nobleman, revolutionary politician, philosopher and writer famous for his literary depictions of a libertine sexuality as well as numerous accusations of sex crimes. His works include novels, short stories, plays, dialogues, and political tracts. ”
oh and “The words sadism and sadist are derived from his name in reference to the works of fiction he wrote, which portrayed numerous acts of sexual cruelty”
This movie was released over 155 years after de Sade’s death, so it’s not like he had any say about the making of the film, but I’d have to wonder if he would approve of the final product and the message therewithin, which is a super watered down version of “doing good only gets you in trouble, if you don’t take advantage of others, you’ll be taken advantage of”. On the face of it, that seems like a message that de Sade would actually get behind, but way they got there in this 1969 film is just too clean without much fuss at all. I’m told there’s a remake from 1977 that’s much more to what I would expect from a de Sade story, but I’m not entirely sure I have the stomach for it.