The first place I really started to articulate my views on aesthetics and ethics came by happenstance on Reddit r/TrueFilm which is a really good source for wading into some good questions about film I've found. So I came across this thread at a time when I was bouncing these ideas around in an aesthetics class so I put together my first real formulation of an answer to this question.
Eventually I'd take a different version of this question as a prompt for a final paper in my aesthetics course. And I very much stole from my own work here in that paper. It was nice to have a low stakes arena to try out some thoughts. It's also nice to not have to write like a philosopher for a while while getting ideas out for the first time.
Often the first take on an argument can be a sloppy, when it catches you off guard. The most complex formulation of the argument I begin to layout here hit me in the stairwell to my building so I sat down right there and jotted it down in my notebook. Amazingly I hadn't really considered my answer to this really blunt question about movies as beginning a fairly novel taxonomy of aesthetics and axiology, but that's really what grew out of answering this question on Reddit.
A Reddit Post
When, if ever, can a film be considered "immoral"? Only when it argues for what we might consider an immoral point of view (Triumph of the Will, possibly Zero Dark Thirty)? When it exploits realistic violence to no greater end than titillation (I Spit On Your Grave) or artistic credibility (Elephant, IMO)? And if a film is immoral, in your view, should it go unseen by that standard alone? -u/ANewMuleSkinner
Triumph of the Will is the key movie for this topic, although I Spit on Your Grave and perhaps A Clockwork Orange also come to mind. I always turn to this piece by Susan Sontag on that movie. She points out some very accurate details, but I think she judges Riefenstahl's work incorrectly.
I for one don't believe that a work needs to be moral to be a good artwork. First and foremost we must separate our ethical questions from our aesthetic questions in axiology. It's a fallacy to say that aesthetics reduces to ethics for example. We shouldn't inquire by moving from some ethical maxim and functionally producing a list of the great works. That would be to say the greatest work is the most moral i.e. here's a maxim of morality, here is a representation of that paradigm. No!
There may be something to it to say that if the work is aesthetic, then there is no ethical nature to it as such. The painting itself has no ethical value. Perhaps when the painting is used as a weapon in a murder it has some moral content, although not because of what is on the canvas. Triumph of the Will so blurs the line because it appears as some accessory to the murderers by validating their parts in the actions. Yet the film itself is pictures on a screen, and we can judge that for a variety of beauties--visual, narrative, and so forth. I value Triumph of the Will very highly on its own, artistic merits. No art is immoral.
But the above is mere speculation. I'd like to answer the question "can a film be immoral?" I'd like to give two affirmative answers. One is the classic answer which will implicate Triumph of the Will, the second is more perverse.
1) A film can be immoral when its existence is germane to the execution of immoral acts. There is a sort of causal relationship between the art and the act. This notion says e.g. there is a Triumph of the Will ergo there is a Holocaust. And I don't think this sentiment is so far fetched. We know the e.g. Holocaust is a terrible act on the part of the Nazi's, and we can consider a set of necessary and sufficient conditions leading to its execution. And we might say these conditions are proxy immoral, they are accessory to the crime. Triumph of the Will might fit under that banner.
I'd like to point out that this first option might very well exclude movies like Elephant or even I Spit on Your Grave from the category of immoral films (it might not exclude A Clockwork Orange by the way). Is there a causal chain present between some extra-artistic act which is immoral and the manipulation of the audience by the movie? If not, the movie may be merely manipulative and not wholly immoral. I think this will be hard to prove but it does point to a rather different option.
2) I do believe a movie can be so offensive that it renders itself immoral. This would be a movie which is not immoral because it gives rise to immorality, but because it offends our sensibilities so much that its aesthetic is an injustice. Manos the Hands of Fate might be an example. Here is a movie which so offends its audience, it is an injustice to watch it. It is torture to watch Troll 2 and it is not something to be inflicted on an unwitting audience lightly. Conversely it is a pleasure to watch Casablanca and something we might desire to experience. I think that this fact has interesting consequence along the lines of distinguishing tastes and offenses. I don't particularly care for The Shawshank Redemption like so many people do, but I do not consider it immoral in this way. When we separate our ethics and our aesthetics, and we judge a work on a variety of beauties, as I said above, it is conceivable that we would come out with a work which we cannot positively value. And this would be an immoral work. Lion King 1 1/2 is a movie I don't believe I deserved to suffer and watching it, for me, feels like an injustice for a variety of aesthetic reasons in addition to the personal insults I feel from it.
I'll point out again, I Spit on Your Grave might fit into this second category by some metric of being gratuitous with its violence, but Triumph of the Will almost certainly cannot be said to be immoral in this way. I favor the view that a movie can be immoral because it is aesthetically deplorable--an injustice to those who look on it--because it lets us be consistent about and say (albeit without perfect certainty) that a movie has moral value because of its aesthetic traits and because it cashes out probable answers for the movies I've considered here.