True. And violence in movies often is gratuitous, just for the shock and awe factor. But sometimes brutal violence is necessary to exemplify the nature of a character. For example, the recent Wolfman movie was very violent - but he was a werewolf. If he was gentle and never did anything horrendous, it wouldn’t make sense for him to despise being a werewolf so much. They had to show it.
But, alternatively, in the recent movie Law Abiding Citizen, I felt they definitely had too much violence. Much of it was irrelevant to the story or character, and could have been done just as well either without it, or with a flade to black cut scene. This also applies to nudity and sexulity. But to address the main point here, as I said art is fictious and fake, but the intent of the creator can determine its moral implications inherently, as shown by pornography. The intent of porn is exclusively to elicit lust or encourage masturbation. Even if someone watches it inadvertently without these intentions, the material itself is wrong. If someone happens to see porn unintentionally, it is not their sin. But watching porn on purpose makes one complicit in the sin of its creator.