I'm with LeMarchand.....I have never once been moved to act violently regardless of what I watch. Are people who only watch romantic comedies and light hearted movies etc always in a good mood and full of joy and benevolence? No, of course not. People were violent in the days before telly etc...this is a very tenuous (and tiresome) argument that is often put forward (particularly in America) as some sort of reason/mitigating circumstance for the latest violent killings. This type of thign has long been said....many will remember 'outrage' over Grange Hill showing drugs use - the hysterical media tried to convince parents it would turn their little angels into drug addicted monsters. This proved to be entirely untrue.
If people have violence in them, it will coem top the surface, regardles sof what external factors influence this. I do agree with LeMarchancd, parental care (or lack thereof) and, particularly in US, the ready availability of weapons, make our culture more violent today, not the tv we watch.