We can judge the message on moral grounds of efficacy by conducting surveys of people who watch the film.
You mean to see how people respond to it? I was more talking about the soundness of the message itself. Suppose we have two equally well-made films, one of which expresses an idea we consider to be incorrect, would it be arbitrary to call it a worse film? If it's not arbitrary, it would be something you can objectively judge even without being a critic.
Messages in films aren't always that clear. Sometimes people can take away an opposite message from the intended one.
The question we have to ask is what most people learn from the film and how it affects their behavior after watching it.
The question we have to ask is what most people learn from the film and how it affects their behavior after watching it.
So you believe that good art teaches you a valuable lesson? A lesson whose strength can be tested by conducting a survey?
Good art is morally good art that is helpful in some way. If it has no utility to make the world better, I regard it as useless.
Even something beautiful can make the world a little better, but if it doesn't inspire changes in actions it's only marginally better than the materials it was made from.
You have to do surveys of some kind to determine if the art actually has the desired effect. It's not a perfect measurement, but we can't just guess at it.