This quote actually has nothing to do with gun violence, but instead with being a vegetarian. Iyengar says that violence is a state of mind not a diet. I'm not sure if I could ever become a vegetarian, let alone a vegan! But getting back on topic, I would have to agree that our states of violence come not from guns, rap music or video games, but from a sickness of the mind.
"Violence is bound to decline when men learn to base their faith upon reality and investigation rather than upon ignorance and supposition."
People no longer search for truth, we simply wait for it to be delivered to us, whether it be through the news or facebook or an app on our phone all we have to do is click and wait. If we bothered to do our own research to improve our well being, our happiness and the quality of our life instead of searching for blame and demanding justice and change, we may improve the root of the problem. We choose to point fingers and scratch the surface, it takes all responsibility away from us. We must not forget we are responsible all the time just simply because we are present.