This is a topic I try to discuss with classes every year on or around April 20 (in honor of Columbine). It makes a great prompt for an argument essay or debate topic.
Below are links to some articles I've used.
One is a short Fox News story from 2005, but the other two are more recent and from NPR. I'm not sure how many you need, but both the NPR pieces have a focus on the reasons for the use of violence in TV. I had my class actually listen to the "Talk of the Nation" program. Before doing this lesson I typed up a couple of the key quotes used and had students discuss each as strong or weak arguments. This program takes callers, so all of the arguments are based on the opinions of listeners then commented on by an "expert." It is a little long, but ultimately pretty good.
Hope this helps.