When is a film a weapon of propaganda, and when is it just simply a visual epic?

Leni Riefenstahl made the film
Triumph of the Will as a propaganda tool for the Nazi party during the Nuremberg Rally of 1934. Although Riefenstahl denied any wrongdoing, it is said that the film served as an important tool of propaganda for Hitler. It was screened throughout Germany in the years prior to WWII.

However, it has also been described as more of an art film, with dramatic scenes and sweeping views of the rally, and Riefenstahl won a medal for artistry at the World Exposition in Paris in 1937, the same exposition that had Picasso’s Guernica.

View Triumph of the Will (It is on YouTube http://www.youtube.com/watch?v=GcFuHGHfYwE )
Do you think this film is an example of propaganda? Give specific examples and explain your choices. When is a film a weapon of propaganda, and when is it just simply a visual epic? Should Riefenstahl be held accountable for her actions in using Nazi propaganda?

Find a contemporary film made during wartime, is it propaganda or not? Explain your position and give examples from the film.