Yes and no.
I have 3 young children and I try to pay attention to what they are watching. While I think that I am very lenient when it comes to what they watch, play and listen to, at times I will tell them they are not allowed to do certain things because of violence, etc.
I think if you set someone down in front of tv or other form of 'violent entertainment' for hours on end, what at first might seem shocking behavior may eventually become acceptable behavior. That doesn't mean I think everyone is going to run out and commit murder after watching Saw or playing Mortal Kombat, but I do think it numbs a person to seeing those types of images.
I know if I tell my children they can't watch, play or listen to something I explain the reasons why. On the other hand, I have let my children watch all of The Matrix movies, Mission Impossible, LOTR movies, etc. Those have violence in them. I explain to my children that it isn't real. How they are actors in makeup or computer generated characters and that no one is really hurt.
So basically, I think if you take the combination of young children, add violent images, then do not talk to them about what they have seen that it does have an affect on them. I don't blame tv for trying to entertain the masses.