The families do not have the universal support of the human rights sector, however. For example, José Miguel Vivanco, director of the Human Rights Watch Americas, opposes a ban in the interests of free speech. This is also the official stance of the Chilean government, which points to freedom of expression as the reason why it does not have the power to stop the event.
This is a difficult issue. It's certainly in pretty poor taste when supporters of Pinochet and similar regimes can continue to gloat about their heroes in front of the victims and their relatives - but I guess that is the point of free speech, you can't just give it to the nice guys. I live in a country - Germany - where for obvious historical reasons it has been decided not to allow free speech in all circumstances concerning recent history. It is illegal here to deny the Holocaust or to display a swastika or make a Nazi salute (there are exceptions to the prohibition on the displaying of Nazi memorabilia for educational purposes - museums aren't breaking the law!). I understand why they've done it, but it's still pretty strange when you think about it, as repressing opposing viewpoints was such a central part of Nazi ideology as well. I'm not sure it's really the answer to memory debates. It would definitely encourage the "victim"/"wronged hero" stance which many of the right-wing supporters of previous miliary regimes seem to hold.
Most of the news reports explain very litte about the film itself. I found this via "paniko.cl":
From this, it certainly looks like the documentary is going to present Pinochet as saviour of a country in chaos, but I would caution that this is just a short clip.
Families of Chile's disappeared condemn homage to Pinochet (Santiago Times)
Chilean government will not stop screening of Pinochet documentary (Santiago Times)
Familiares de DD.DD piden al gobierno que intervenga para evitar homenaje a Augusto Pinochet (La Tercera)