Let me reiterate. Violence is not the answer for one reason and one reason only. Once it starts and everyone joins, it will be very, very hard to stop.
edit: be
The gunman made his own gun, in a country with ultra-strict gun laws. The Unabomber made his own bombs. The Seattle mall Islamist knife attacker refused to stay down after being shot multiple times.
My takeaway: political terrorists are particularly motivated. Secondly, gun laws slow them down but don't stop them.
It's not some statistical difference between almost no violence and no violence. It's night and day. Orders of magnitude. Teens walking back from parties through the middle of the city at 1 am with their parents permission vs clan wars.