Viridiana?
Banned by the Catholic Church (something I have actually heard about rather then googling..). If I remember, in particular a scene in which drunk people mock the last supper particularly drew the Vaticans ire.
Good guess but no, I'm afraid. I may add that one to my watch list.
The final clue I can give would be that a riot broke out at its premiere. I don't know how much more I can say without giving the plot or the director's or actors' names.