I think I might take a slightly different approach than the rest of you guys. I'll address the questions Felipe raised, but to me it seems necessary to not simply think about whether propagandistic messages are welcome or effective in films, but also to investigate the manner in which politically conscious individuals make films.
Ask not what the cinema can do for propaganda, but what propaganda can do for the cinema!
This goes back to my buddy Dziga Vertov. There's no question that Vertov held socialist ideals in high regard. But his films weren't just a bunch of slogans and posters and whatnot. His ideology actually dictated how he viewed and used the medium. For Vertov, cinema had to function as an extension of the Communist decoding of reality. I think it's interesting to see how the boundaries of the art can be pushed for political goals.
"We're definitely not in Cannes anymore...actually, we've never been there."