I think sometimes music gets wrongly blamed for it's influence. I remember after the Columbine shooting the media was discussing the kind of music the shooters had been "influenced" by, Marilyn Manson, heavy metal, etc. While I can agree that music has an influence on us, on our mood or state of mind, I have a hard time putting the blame on the type of music. I think first and foremost it's the person that is to blame.
I watched an interview of Radiohead's lead singer Thom Yorke, in which he talks about why it's important not to confuse the personality of the art with the personality of the artist. I'm thinking back to our class discussion of "Pumped up Kicks" and how people are angry that the lyrics tell such a violent story. But in my mind it's just that, a story. Making the connection between the content of the song and the personality of the artists, or the idea that these types of lyrics are promoting the sort of action they are telling about, is missing the point entirely in my opinion.
Having said that, I do think it's the responsibility of the person not to allow music or art that contains a negative message to influence their actions. Just because I go to see an action film about violent bank robberies doesn't mean I'm going to go out the next day and rob a bank. I think the overwhelming majority of people have the ability to make this distinction, which is why I think it's unfair to blame music when once in awhile someone with mental health issues decides to do the irrational thing.