They have blamed all sorts for the columbine. They had videogames, films, tv shows (Specifically South Park- Ironic as the inventors of South Park came from Columbine High School), music and their main target for influence was Marilyn Manson, who got banned from about 48 states until the mother of the offenders stated that the students had never listened to Marilyn Manson in their life, and he was just targeted as he was doing a gig nearby at the time. Even a year after this was found out he wasn't allowed to perform at a venue in Columbine as part of the Ozzfest tour, the council didn't allow it. Meanwhile, the council did (Ironically) allow head of the National Rifle Association Charlton Heston to visit the town and deliver a speech about the fact that guns are a useful way of defending yourself.
Now, who do you think is a bigger influence? The president, who ordered the longest one day bombing ever on the very morning, 2 hours before the columbine incident? The world's largest nuclear missile manufacturer, whose main factory is situated in the town of Columbine? The head of the NRA, who was allowed to visit Columbine by the local council (Despite the protests saying that he WAS an influence of the cloumbine incident) and talk about gun ownership and how good it is? Or a heavy metal singer, who sings some offensive lyrics, who the kids had never even heared of, and who just got all the blame from it?