Whatever you think of de Sade, he was a complex figure and we should not look for easy answers with him. He was, strangely perhaps, against the death penalty, and he was never put in prison for murders or anything like that.
It just seemed to me to be a great story, set back in its time but something that seemed to have relevance for our time. Now that the film is coming out, it looks like we're back in another time where repression of expression is all the rage.