After a North Carolina Republican Party office was firebombed last week, news media denounced the political Left's tendency to turn violent.

Ha ha, no, of course they didn't. Instead they stuck to what they know best, blaming Republicans and insisting that the Right is prone to violence.

On his show Monday night, "NBC Nightly News" host Lester Holt spent a segment not on the actual violence perpetrated in the firebombing against Republicans, but on " undertones of violence" that allegedly lurk within Donald Trump's presidential campaign. The segment included clips of fights at some of Trump's rallies but didn't mention that much of it was caused by supporters of socialist former Democratic presidential candidate Bernie Sanders.

This was in a week, moreover, in which two Democratic activists, one the husband of a member of Congress, were implicated in sending rent-a-mob provocateurs to start violence at Trump rallies.

So the Left organizes and pays people to tarnish Republicans in general and Trump in particular with violence, and the press dutifully wrings its hands about undertones of violence.

People on the Right sometimes resort to violence, but it is hard plausibly to argue that they are responsible for most, or even the majority, of it.

News media downplay left-wing violence not just because they tend to support left-wing causes and so avoid negative reporting, but also because they swallow flimsy left-wing rhetoric that presents disruption, intimidation, and sometimes assault as legitimate democratic action. When right-wingers are violent it generally isn't camouflaged by bogus political principle.

But you still find sympathy on the Left for such movements as Occupy Wall Street, which was presented as a protest against big banks but was always (or at best swiftly became) a parade murder, sexual assault and violence against the police.

Contrast that with Tea Party rallies and the way the media portrayed them. They were almost entirely peaceful and put on by people who even picked up their own trash. Whenever a fight did break out, news media would conclude that it was "a symptom of the polarizing rhetoric that fueled" the Tea Party.

These days, protests against the police routinely involve street violence, shutting down highways, vandalizing police stations, and destroying local businesses.

It's true that no movement, whether it be Black Lives Matter or any other, can control all the people it inspires. In July, after two black men were killed by police in Baton Rouge, La., a gunman took advantage of a BLM protest to target and kill five police officers. Other officers have been targeted as well by fanatics who cite its inspiration.

But the smashing of city centers, even though it is depicted as extreme, nevertheless is tinted with media sympathy for the cause. There is no such indulgence but, rather, hair trigger condemnation when there is any unrest associated with the right, particularly the GOP's presidential nominee.

News media need to stop pretending the violent left-wingers are just rowdy kids going too far in a good cause. When firebombs are thrown at Republicans, Republicans are not to blame.