I will say this. Romans used to watch people each other in coliseums. Bare Knuckle boxing has been around in every culture. Hunting has always been a big part of human nature. We aren't getting more violent nor is society collapsing, The difference is these days violence is more socially unacceptable leading people to freak out when it does happen.
I'm not saying it is okay to going around killing people, but I don't think its a new trend.