As everyone knows, it's very hard to distinguish what is the cause and what is the consequence - are films more aggressive and violent because society has become that way? Or does the constant violence and aggression portrayed in the media fuel sensibilities?
Basically, where there is peace, there is fighting. Violence is part of the human psyche. Some act on it, some can contain it. But we all need outlets. Film is an outlet for an angry world. Anger is bred from fear. We live in a world of constant fears, partly spurred on by the media.
I have watched violent films and more often than not, they are violent to actually portray how awful it is, how demonising it is. It is so we can react against it, not commit it. Video games are a little more sketchy. For those who play it and aren't stable enough in mind and morals not to committ violence can be influenced. I have played many a violent game but am not an aggressive person. I never will be. I know the difference between reality and fantasy.
On the other hand, I know people who never play video games or watch violent films but are the most bad tempered and aggressive people I know - terribly so.
This world is suffering from an epidemic of aggression. With a planet of 6 billion people fighting for survival, we have lost respect for life and peace. The more people you have, the higher ratio of uneducated and ignorant people as well. Those people are likely to be extreme and therefore aggressive. That is not always the case.
Pacifism doesn't work in a practical way. The world is all about war - who has what weapons, who has more power, and these are all elements of aggression. We live in a bullying environment. Look at Tibet.
Aggressive films can effect those who are hot headed and that is not good. But others will also be appalled. Violence for the sake of violence is absolutely abhorrent, such as the Saw films - gore fests that do nothing for society, do nothing for humanity and are cheap experiences. Films like that should be discouraged. But films that depict violence because there is a point, such as war and conflict and repression etc, or because the society represented is brutal, i.e Ancient Rome in Gladiator, is fair enough.
But too many films go over the top for no real reason. This only reflects the society in which we live. I wouldn't deny anyone to watch gore fest movies like Saw if they aren't aggressive themselves, but it does make one wonder why human beings want those images in their head just for the heck of it?