The real answer is that they are all responsible.
Matt Bracken addressed this in a short piece he wrote a while back called " What I saw at the coup" - about how a bunch of leftists are brought down when their little revolutionary stunt is called out with gun shots:
https://westernrifleshooters.wordpress.com/2012/09/11/what-i-saw-at-the-coup/
It's fiction - but he's got a point. When the politicians and their mouthpieces start dying for their little escapades - it might force them to think twice about it. As it stands now , the cops hide behind their thin blue wall and government power - and the politicians and all the rest of them hide behind the cops and military power.
Not for nothing - but this is all EXACTLY why we have a second amendment.