Dallas knows a thing or two about assassination conspiracies. We know that the more important conspirator is usually the political climate, not the shooter.

Properly stoked with hate, violence and dehumanizing vilification, the climate will find its shooter. A Lee Harvey Oswald will step forward to kill JFK or a Yigal Amir will volunteer to murder Yitzhak Rabin, as Thomas L. Friedman argued forcefully two days ago on The New York Times op-ed page.

More than 30 years ago I interviewed the late Stanley Marcus, then recently retired as head of the Dallas-based Neiman Marcus retail store chain. He had lived through the years of extremism in Dallas preceding the 1963 assassination here of JFK by Oswald.

When I interviewed him in the mid-1980s, the popular belief was that Oswald had acted as a cog in some larger as-yet unearthed conspiracy. That basic concept was an almost unshakeable shibboleth, a cultural assumption fervently held by many if not most Americans. What Marcus wanted to get across to me was that the reality was far worse than a conspiracy, less neatly satisfying, much more broadly incriminating.

After all, if JFK’s murder was a classic conspiracy, then the only thing Dallas needed to do was prove it wasn’t in on it. But Marcus, who had played the role of community conscience throughout a long and illustrious career, wasn’t about to let his hometown off that easy.

“Following the assassination,” he told me, “there was a great desire on the part of the leadership to cope with the situation. The word, cope, was the way to describe it. And everyone was saying, ‘Well, it could have happened anywhere.’

“Of course, that was true,” Marcus said. “But it did happen here, and it happened partially because of the atmosphere that attracted that kind of fanatic nut. And when a community doesn’t do anything to express disapprobation, it is logical that it will attract more and more of them.”

Marcus gave me verbal portraits of events in Dallas preceding the assassination that feel, as I reread them now, like mirror-images of the dark raucous scenes published by The New York Times last week in a video called, “Unfiltered: Voices from Trump’s Crowds.”

Marcus was with U.S. ambassador to the United Nations and former presidential candidate Adlai Stevenson in Dallas on October 24, 1963, almost one month to the day before JFK was murdered here. In the mid-1980s when I wrote about my interview with Marcus, I said, “To this day, his eyes widen when he calls the scene to mind.”

In 1963 he and Stevenson were getting into a car when they were surrounded by a mob. “I pushed him into the car,” Marcus remembered, “and they surrounded us. They were rocking the car.”

In the months before the Stevenson incident, Vice President Lyndon Johnson and his wife, Lady Bird, were attacked and spat upon by a Dallas mob. Arkansas Senator J. William Fulbright declined invitations to come to Dallas, telling friends he feared violence.

The climate of extremism was in no sense limited to public events. Even though he was a recognized leader in the community, Marcus told me he had found social life difficult in the period before Kennedy was killed.

“I found it very difficult to go to a dinner party without getting into violent discussions. If you disagreed, you were automatically labeled a communist.”

As for what stirred this cauldron of hate, Marcus awarded a good share of the blame to local media, especially The Dallas Morning News, holding the newspaper responsible in large part for the atmosphere that preceded the assassination and for the assassination itself:

“I have always charged that The Dallas Morning News then was as responsible and as answerable as any single institution, because they never repudiated it.” (For more about the political climate in Dallas and the role former Morning News Publisher Ted Dealey played in ratcheting up the heat, see the book Dallas 1963, by Bill Minutaglio and Steven L. Davis. For a sample, check out our excerpt from 2013, "How the Morning News Helped Dallas Become the City of Hate.")

And there it is, really — the key ingredient, the fulcrum on which history bends one way or the other. The repudiation. It’s that John McCain moment in 2008 when he drew boos and jeers from what had been an enthusiastic crowd by telling a woman that Barack Obama was not a dangerous alien.

“No, ma'am,” McCain said. “He's a decent family man [and] citizen that I just happen to have disagreements with on fundamental issues and that's what this campaign's all about."

Would that have been enough here in 1963? We can’t know. But if Marcus was right, if the local climate of intolerance and extremism was the tuning fork that resonated with the mad internal orchestra inside Oswald regardless of political ideology, then what might have happened if someone had forcefully sounded another conflicting note? Nothing? How do we know that?

What we do know now in our own time is that the madmen who attack us in bars and movie theaters or on the streets of downtown all sing a very similar predictable almost ritualized tune. Just for the sake of argument, let’s forget about their claims to politics — almost always a garbled and self-contradicting inarticulate mish-mash anyway.

Instead of listening, let’s just look at them for a moment. We see the fake-soldier garb, the stockpiled weapons, the stealth, the wholesale slaughter of strangers. In fact, if we keep looking and look a little deeper, into personality, we see strong similarities — the churning unresolved turmoil loosely gathered under some pseudo-philosophical umbrella. We imagine them stooped and muttering, filled with explosive wrath.

These people are from central casting. It’s not possible — not for me anyway – to look at this plague of public shootings and not see ritual, one acted out in public at an accelerating tempo, in which the same kind of loosely moored soul steps forward each and every time, as Oswald did to shoot Kennedy, as Amir did to kill Rabin, because they have seen it all on television before and have heard the call.

And each time it happens, we make the same foolishly self-exculpatory mistake. We look for some hard-edged conspiracy to explain what happened.

We are relieved a little, are we not, when ISIS takes credit, even though we know ISIS would take credit for a tsunami if it killed the right people. If there is a conspiracy, after all, then that will mean that we didn’t do it.

And that, by the way, is the thing we know here in Dallas, the inconvenient truth. We are all conspirators when we fail to repudiate the climate that sends up the drumbeat call to violence.

I don’t know about you, but I’m sick and tired of personality profiles of Trump. I can’t read them anymore. I’d rather read the personality profile of a tree stump.

We know what he is. He ducks and dodges, smirks and winks, brags about how much he wants to beat people up, tells jokes about the gun lobby and stopping Hillary Clinton. Mainly he pokes, stabs, waves and cheers the crowd on with that shrug and Mussolini look-away, that gesture that means, “You know what to do.”

He’s from central casting, too. Is there anything surprising or even terribly interesting about the man? He had to happen, did he not? Given the rise of right-wing extremism that began more than eight years ago with the first Obama candidacy, some kind of Trump or another had to wander into the spotlight and start wriggling around in it like a fat baby.

The increase in extremist rhetoric at his rallies and now these ever more transparent exhortations to violence: I don’t believe there was ever a way to avoid any of it. It was always there in the belly of the beast, waiting to be vomited up.

What’s missing is the repudiation. What’s missing is the John McCain line (notably from McCain, more’s the pity): No, sir. She's a decent family woman and citizen. We just happen to disagree on trade policy.

That’s the fulcrum, the point of resistance that will bend the future to the good. Or not.

Marcus knew that if leadership does not effectively repudiate a climate of extremism, then eventually that climate will discover and recruit its Oswald. The climate alone will send him or her on the climate’s mission. Nobody needs a meeting or a secret code. It’s all right there in front of all of us, as we speak, happening in real time.

