Even the perception of danger is usually enough to trigger a violent reaction. Also violence for its own sake can be a very emotional and immersive experience for both the participants and the spectators... Full Metal Jacket is a great movie, Rocky sucks but is somehow still a great movie...
It's like I tell my boy, if you want to go and fuck up some complete stranger... shoot em, stab em, whatever, it's okay as long as someone in the Army tells you it's okay, other than that, you may wind up in jail. Also, you can't tell the recruiters that you want to murder another human being and that's why your joining thier ranks, they would think something was wrong with you and probably have you arrested.
The problem with giving peace a chance as the primary reaction is that under some circumstances violence is seen as a justifiable action especially as a response to a violent action. You punch me, I'm going to punch you back really hard. I love Ghandi but if he punched me I'd kick that little bastards ass... and it'd be immediate, I wouldn't debate, I wouldn't hesitate, the second his hand left my skin, I'd smack him like a scalded cat.
As a nation, we did the same thing... we got punched in the gut and in our rage we lashed out and killed the children of our neighbors. Turns out... we were wrong... we were lied to... we were mislead... blah blah blah... we were stupid, just as stupid as our fathers and thier fathers before them... stretching back through all the ages of Man, it's who we are... we as a people are no better than our least common denominator, down here in the dirt where I live, violence is alive, it's a part of everyday life so before you can fix violence at the macro level, we need to develop a solution for the microlevel.