Religious conservatives tend to believe that people are far more easily brainwashed than they actually are. I have my suspicions as to why they believe this, but we'll leave that for another thread. But because they tend to believe this, they have a tendency to blame ideas for behavior more than is realistic, I think. It's why they want prayers in schools so badly: because they actually believe that making kids say prayers in school will help brainwash them into believing what they're being made to say. And it's also why they fight so hard against any alternative messages or ideas. They don't seem to understand that most people can listen to an "evil" message and not become evil themselves. Most people do not automatically assimilate content like that.
On the other hand, they do have a point. Angry people listen to angry messages, because that's what "makes sense" to them. They identify with angry and violent messages because they are angry people, who like the idea of satisfying anger with violence. And it is true that the repetition of these messages tend to dull people's culturalized taboos against such inclinations, which can increase their likelihood of acting out violently.
But some Christians are angry people, too. And so they like angry and violent messages just as much as any angry non-Christian person does. And they can find plenty of them in their bibles, or in their preferred music, reading, etc. Religion is full of anger, vengeance, and violent messages.
But it's always easier to see the flaw in someone else's behavior than it is to see it in our own, and Christians are certainly no exception in this. In fact, I think we often focus on the flaws of others so that we can more easily ignore our own.
But this all works both ways. Just as Christians should look closer to home when they want to go looking for negative cultural messages, so the same is true of those who like angry and violent non-Christian music, and books, and etc. Perhaps it's time to ask ourselves why we favor this sort of negative and destructive imagery, and ask if it's really all that healthy for us to be surrounded by it.