The usual cultural suspects have been rounded up in the wake of the Virginia Tech shootings, with Hollywood under renewed scrutiny after Cho Seung-Hui's rampage left 32 people dead. Claims that the bloody South Korean revenge movie Oldboy may have served as inspiration to Cho re-opened a debate about whether violent films cause violent acts. The response from two of the filmmakers most responsible for spawning Hollywood's modern-day horror movie industry, Wes Craven and John Carpenter, is emphatic. 'If someone has violent thoughts, they're going to be attracted to things with violence in them,' says Craven, creator of the Nightmare on Elm Street films and 1970s shocker The Hills Have Eyes. 'But are those things making them have violent thoughts? I don't believe so. Horror films and violent films aren't a cause of violence itself.' Carpenter, speaking at a panel discussion at the Tribeca Film Festival in New York, says Cho's spree reflects the violence of society. 'Real life causes this,' he says. 'Fake life doesn't cause it.' But a series of extraordinarily gruesome films of late - such as Hostel, Saw, Wolf Creek, The Devil's Rejects and Turistas - has left even liberals wondering how much further the envelope can be pushed. The films have even been given their own genre - 'torture-porn' - reflecting the fact that many of them have scenes depicting young women being subjected to sexual violence before being butchered. Some say the time has come for the Motion Picture Association of America (MPAA) ratings body to get tough. Thomas Doherty, the chairman of film studies at Brandeis University, says there's been an 'utter collapse of censorship restrictions on matters of violence'. 'I wouldn't censor films like Hostel and Saw,' he says. 'But if I were on the classification and ratings administration, I'd start giving them NC17s.' That bars anyone under 17 from seeing the film. Presently, most gory movies are given an R-rating in US cinemas, meaning anyone can see them provided they're accompanied by someone over 21. Already there are signs that the MPAA's patience is wearing thin. The makers of the movie Captivity were reprimanded over a recent poster campaign showing a woman being kidnapped and tortured, with the movie's tagline: 'Capture, Confinement, Torture, Termination'. The ad campaign was turned down by the MPAA's board of censors. The film must now wait a further month before it obtains a rating. Joss Whedon, the creator of TV series Buffy the Vampire Slayer, wrote an open letter to the MPAA decrying the Captivity campaign, describing it as 'not only a literal sign of the collapse of humanity, it's an assault'. 'This ad campaign is part of something dangerous and repulsive,' he wrote. 'And that act of aggression has to be answered.' For Craven, however, the emergence of torture in the mainstream is a direct consequence of the US government's sanctioning of controversial interrogation techniques at facilities such as Guantanamo Bay. 'It doesn't surprise me that there's a lot of torture in horror films, because it's coming out more and more that it has been happening, whether it's Iraq or the CIA taking people off to secret prisons,' he says. 'That's the reality - so it's going to creep into films.'