The right -- the modern American right -- has a very troubled history with political violence. The ideological pattern is clear going back at least thirty years and arguably far longer. A simple review of the 1990s, particularly 1993, 1994, culminating in many respects in the tragic 1995 bombing of the Oklahoma City Federal building in April 1995 tells the tale. Mix in the militias, the thankfully inept attempt on President Clinton's life a few months before Oklahoma City (see Francisco Duran) and it's all really not a pretty picture.
Wait, what? Yes, the OK City bombing was a horrific and awful event which arose from a virulent strain of libertarianism. To argue that came from the "modern American right" is like blaming the "modern American left" for the violent actions of hundreds of left-wingers. He's attempting to blur the lines between mainstream Conservatism and a bunch of crazies.
And then he throws in Francisco Duran, who fired at the White House. Duran claimed he was incited to violence by listening to an ultra-conservative named Chuck Baker (so popular you've never heard of him). He also claimed he "was trying to save the world by destroying an alien "mist", connected by an umbilical cord to an alien in the Colorado mountains". He sounds like a regular ole Republican Senator doesn't he?
Let's think about left-wingers who committed violence. I'm having a hard time finding any. Hey, how about about that guy in Dallas with the gun?