In some cases censorship has been used as a way to suppress alternate ideas or indeed impartial home truths (think Stalinist Russia). How can one measure the negative influence of any form of media? You really can't. That means we have no idea whether or not its overall impact can be a negative for society. Even theorists in this area have problems. For example, Stuart Hall and John Fiske. Taking the ideas of former like "encoding and decoding" whereby one part accepts the belief that the audience understand and engage the medium but also in another accepts that at times they do not. There is kernel of truth in there, mainly, IMO, that different people can interpret media in different ways.
I do think panic about movies and computer games is manufactured moral panic and serves a purpose other than the protection of society and our morals.
Go back seventy years and people would have been saying the same thing about The Beatles.