Media assumptions that violence is right-wing are routine — and routinely wrong.

On Friday morning, Brian Ross of ABC News speculated on live TV that James Holmes, the accused killer in Aurora, Colo., was a member of the Tea Party. A few hours later, Ross posted a short apology online; Holmes had no Tea Party connection.

Ross’ unfounded speculation wasn’t unusual (although the speed of his apology was). This was merely the latest case of media commentators jumping to the conclusion that violent attrocities should be attributed to members of the political right. Let’s look back at how often the media has falsely invoked Tea Partiers and other “right-wing nut jobs” in the past few years.

* September 2009: The discovery of hanged census-taker Bill Sparkman in rural Kentucky fueled media speculation that he’d been killed by anti-government Tea Partiers. In fact, he’d killed himself and staged his corpse to look like a homicide so his family could collect on life insurance.

* February 2010: Joe Stack flew his small plane into an IRS building in Austin, Texas. The media immediately suggested that the anti-tax rhetoric of the Tea Party led to the attack. In fact, Stack’s suicide note quoted the Communist Manifesto.

* That same month, a professor at the University of Alabama, Amy Bishop, shot and killed three colleagues at a faculty meeting. The gun-loving Tea Party came under immediate suspicion. But Bishop was a lifelong Democrat and Obama donor.

* March 2010: John Patrick Bedell shot two Pentagon security officers at close range. The media went wild with speculation that a right-wing extremist had reached the end of his rope. Bedell turned out to be a registered Democrat and 9/11 Truther.

* May 2010: New York authorities disarmed a massive car bomb in Times Square. Mayor Bloomberg immediately speculated that the bomber was someone upset about the president’s new health-care law. The media trumpeted the idea that crazed conservatives had (again, they implied) turned to violence. In fact, the perp was Faisal Shahzad, an Islamic extremist.

* August 2010: Amidst the debate over the Ground Zero Mosque, Michael Enright stabbed a Muslim cab driver in the neck. It was immediately dubbed an “anti-Muslim stabbing,” with “rising Islamophobia” on the political right to blame. In fact, Enright, a left-leaning art student, had worked with a firm that produced a pro-mosque statement.

* September 2010: James Lee, 43, took three hostages at the Discovery Channel’s headquarters in Maryland. The media speculation was unstoppable: Lee was surely a “climate-change denier” who’d resorted to violence. Oops: He was an environmentalist who viewed humans as parasites on the Earth.

* January 2011: Jared Lee Loughner went on a rampage in Tucson, Ariz. Again the media knew just who to blame: the Tea Party and its extremist rhetoric. In fact, Loughner was mostly apolitical — a conspiracy theorist who, to date, has been judged too mentally incompetent to stand trial.

The media’s habitual blaming of the political right is endemic and incurable. Media figures sincerely believe the right wing is violent, so naturally assume that violent people must be right-wing. This won’t be the last time they make that mistake.

Gabriel Malor is a lawyer and blogger in Washington, DC.Twitter: @gabrielmalor