if the argument is that he was simply defending his right to walk around with a gun, i wouldn't accept that. i would support the police shooting people walking around with weapons in public and would not support the idea that that's some kind of right. that's utterly retarded.
they might have perhaps shot him in the leg, instead. it seems like this was probably overkill, and the last several years of events in minnesota suggest there's a systemic problem in the police force in minnesota.
but i would, in principle, support shooting at people at protests with guns, and i would support that as a protester. it's not something that's ever come up here, but if i showed up to a protest group and there was a guy with a gun, i'd be on the other side of the square. i wouldn't go anywhere near him, wouldn't talk to him and would want him to go away. this guy showed up to a rally prepared for a war. that's not to say that the united states won't get to civil war in time, but it's not there, and i'm certainly not in support of people trying to get there.
the difference between the united states and iran is pretty overwhelmingly clear. in a democratic society, all civil disobedience should be non-violent. americans don't need to use violence to tear down a dictatorship and create a democracy, they have a system to work in. it's hard, but americans have what the rest of the world is fighting for, and there's no justification to use force when you lose an election and don't get what you want.