"Inspired" seems perhaps too strong a word for the connection.
Can you say that, had Natural Born Killers not been made, there would have been no Columbine? I contend that it would have happened anyway. If that movie didn't exist, they would have found another movie to imitate, or even one of the other things they were interested in, such as DOOM or whatever. Correlation not causation.
Sure, you could remove both Natural Born Killers and DOOM and KMFDM and whatever else, but then they would have moved to something else. You can't ban everything just because some sick people might enjoy it.
How many mass shootings have been inspired by the bible or the quran, or The Catcher in the Rye?
Even if media (social or otherwise) can influence people to commit violence, does that justify censorship?