An article with a good complication of political violence: http://www.tobytoons.com/td/left-wing-assassins.html that you can pass out to your lib friends.
When will the people of America wake up and see most of the violent political acts come from in this country? One side of the political aisle is perfectly OK with violence as a means to an end in politics (generally).
First the dude near the RNC convention with the machete, now this, plus add to it all the similar type of facebook pages against Sarah Palin, Rush Limbaugh, etc.
Look at the leftist political regimes in the past too.