If humans can not be influenced by what they read and watch, why do business spend billions of dollars each year on advertisement.
I do not believe portraying violence per se is the problem (our literary and before that oral histories are full of violence).
The difference then and now there was a moral point to the violence. The good guys won and the bad guys lost. Today, the entertainment industry routinely allows the bad guys triumph over the good guys, or they present those who should be the good guys in our culture are presented in the worse possible light.
So do movies influence people, well asked the t shirt people after Clark Gable took off his shirt in it happened one night.