There are multiple fallacies and outright lies in the OP.
To begin with, the use of the word "violence" is gratuitous -- it isn't even defined. Calling for the USA to enforce its laws against treason and sedition does NOT constitute "violence." The call to repel those who would attempt to overthrow the US, from within or without, is NOT violence. I note they don't actually QUOTE anyone on the Right, except for O'Reilly calling for the arrest of a traitor (not tarring and feathering).
The statement "I began to realize that the last significant violent turn in American political ideology and practice involved both the political right and the left" is completely disingenuous. The Weather Underground, SLA, Black Panthers, etc. etc. were all a creation of the Left. At that time, the tiny fringe of White Separatists were not part of the national milieu. And the OP doesn't even bother to list any political right sources of so-called (and still undefined) violence.
And this statement "This, however, is not the political philosophy that guided the framers of the U.S. Constitution" is so ignorant as to remove any credibility from this already un-credible writer. Starting with "Give me liberty or give me death," the entire birthing of this country was accomplished through violence and violent talk. The framers understood the importance of might and the use thereof.
And the Left licks this stuff up like the rest of the sugar-colored shit they so love.
