As a culture we love to watch violence. We are addicted to violence and as a consequence addicted to trauma. Media outlets have long understood that “if it bleeds it leads”. The Classification and Rating Administration is more tolerant of Rambo massacring scores of Vietnamese than it is of a nice naked body on the screen. Most US presidents have waged some form of aggression on another country (except Jimmy Carter and look what happened to him).
Violence feeds our need, as traumatized people, to maintain a higher level of adrenaline. Like a professional athlete we need to maintain this high chemical level. 
And through the fear and anxiety that these violent programs and news feeds and government actions gives us, our bodies get the fix. Our state of fear is elevated, cortisol and adrenaline is released and our heart rate quickens.
The emotional response to trauma is a chemical one and as we know, consistently high levels of these drugs can have serious health consequences. Like all addicts who crave their drug, there is a real chance of overdosing.