Except there isn’t. Timothy McVeigh, an atheist, wasn’t part of the conservative or libertarian movements. He wasn’t even part of the militia movement. And what on earth was right-wing about the Columbine shootings?
In plenty of cases of multiple killings, from the Unabomber to Christopher Dorner, the perpetrators espoused views closer to the mainstream left’s than McVeigh had to the mainstream right’s. Occupy Wall Street was an idealistic expression of democratic protest, but the tea partiers are brownshirts in khakis.
And, recall that Secretary of State John Kerry belonged to a group — Vietnam Veterans Against the War — that once discussed assassinating American politicians. Barack Obama was friendly with a convicted domestic terrorist. But to even bring these things up, never mind invest them with significance, is considered outrageous guilt by association.
And you know what? Maybe it is.
But if that is outrageous, what do you call the paranoid style of liberal politics that has confused normalcy with fascism for more than half a century?