"Here's What Happened the Last Time the Left Got Nasty" is the headline on an article in Politico by David Greenberg, a media professor at Rutgers.

The last time was the 1960s. The artwork accompanying the story: the Greenwich Village house that has just been blown to bits by a Weather Underground bomb that exploded prematurely, killing three members of the radical organization.

Greenberg's main point, as the choice of art for the story indicates, is that the left is hurting itself.

It is an article well worth reading.

Greenberg recalls that Julie Nixon was prevented from having her own father present at her college graduation because of the political atmosphere in the country. Julie Nixon herself wrote to John Ehrlichman, “I truly think the day will be a disaster if he comes,” given the anticipated protests.

Greenberg writes:

Hearing these stories, many will respond: Boo-hoo. What’s Julie missing her father at graduation compared to the strafing of Cambodia? But the point is not that Julie Nixon or Robert McNamara was done a grave injustice, any more than discomfort with the treatment of Sarah Huckabee Sanders and Kirstjen Nielsen means seeing them as victims. The reason to maintain standards of conduct and preserve a nonpolitical space of human interaction is not to protect particular politicians and government officials. It’s to protect America, to uphold the political culture we value.

Trump and his followers have already shown their contempt for the practices and gestures that help us live amicably with our ideological opposites. Joining Trump in the project of trashing the unwritten rules of public conduct won’t change his policies or governing style.

But it will betray our own values and make it harder, once he’s gone, to reconstitute a decent, humane politics. We have nothing to gain from the eradication of a politics-free zone, from a war of all against all that greenlights once-verboten behaviors and permeates once-private spaces.

Besides, as the events of the late 1960s and early 1970s show, the outrageous and obnoxious antics of the militant left ended up hurting their cause. The taunting of public figures isn’t well remembered, and neither will history long record June’s showdown at the Red Hen.

But insofar as these actions stem from a determination to score political points by violating civil norms, they—and the repellent and violent methods of extreme protesters more generally—engender a backlash and alienate allies. By 1972, we should recall, a majority of Americans had come to oppose the Vietnam War, but greater numbers opposed the antiwar movement.

I just want to make one objection: Yeah, the President can be crude and make one cringe. But this vitriol began long before President Trump. It was present during the George W. Bush administration, when it was permitted on the left to say absolutely anything, and even to publicly indulge in assassination fantasies, about Bush.

It accelerated during the Obama years, when the President did little to calm the waters when activists turned on the men and women in blue who risk their lives to protect us.  I wish President Trump would cool it sometimes, but I don't hear him or his most ardent supporters using the F-word and refusing to eat at the next table from people who disagree with them. Maybe it happens, but I haven't seen it.

But Greenberg is right: it is time to uphold the decent political culture we value.

And he is right–the left is hurting itself.

But it is also hurting the rest of the country by creating a tinderbox atmosphere that could burst into flames if so many continue to play with fire.

We should all be careful not to behave in a way that hurts our cause–and our country.