South Korea has already mentioned plans to take this film, put it on dvd, and float balloons across the border to incite rebellion in the population. By trying to prevent the movie from being distributed at all, North Korea is essentially trying to avoid anarchy caused by external propaganda.
If a bad movie can incite rebellion in your country then your country is in a terrible, terrible place.
Why are we so eager to overthrow their regime?
Why do you think making a movie was an attempt to overthrow their regime?
Is democracy so sacred that we must ~force~ it on every country around the world? What business is it of the US (and Hollywood) to decide what is the best system? What they have there is what developed in that region. It is a system that won out over the infighting to unite their country. It might not fit our definition of "fair" for the population, but that's only our definition. It's our own view that we're extending upon them, a culture that has had to isolate itself just to keep together.
If there ever was an argument for pushing democracy on a foreign country North Korea would be it. North Koreans aren't citizens, they're prisoners, they'd actually be better off living in Orwell's 1984.