“Oh, but I don’t believe in ‘conspiracy theories,’” the nervously shaking nebbish replied when someone gently tried to introduce him to a plausible alternative to the official, prevailing wisdom about who killed Kennedy.

It is curious, indeed, that the association of the term, “conspiracy theory,” with an automatically derogatory meaning first came into fashion in the years following the assassination of President Kennedy 50 years ago this month.

Quickly, the phrase emerged to become a way to summarily dismiss anything but the official version of that assassination, which hinged on the Warren Commission’s conclusion that Lee Harvey Oswald “acted alone.”

A “conspiracy,” you see, involves by definition anything in excess of one person. It can be two people acting in collusion to do just about anything. Many great events in our history involved far more than two people acting in collusion. In fact, it’s hard to think of any acts of importance that were truly the work of a single actor.

Even President Lincoln’s assassin, John Wilkes Booth, was part of a conspiracy. There is no doubt that the U.S. CIA engaged in coordinated assassination attempts, often successful, against foreign leaders it didn’t like.

What has made modern, domestic assassination attempts more cloudy, often more difficult to assign to a “conspiracy,” has been the post-World War II CIA efforts at creating a “Manchurian Candidate,” based on using mind-control methods to induce someone to act against their own will and on behalf of a CIA objective.

There is no doubt from the data that arose out of the Rockefeller Commission and Church Committee hearings in the mid-1970s that the CIA was hard at work with such efforts right up to the point that President Kennedy fired the dull-witted right winger Allen Dulles as head of the CIA in 1962.

How ironic that, following Kennedy’s assassination, the same Allen Dulles would come back to play a pivotal role in the workings of the Warren Commission that concluded Oswald acted alone!

It should be needless to say that the credibility of something someone may dismiss as a “conspiracy theory” has to do with evidence presented, not with whether or not is runs counter to official versions of events. But the “conspiracy theory” technique for discrediting anyone who proposes to introduce such evidence has developed into a full blown science of its own, delving into the ostensible psychological weaknesses and socio-political origins of persons holding to them.

In other words, evidence pointing beyond official explanations are now counted as “crazy” and “crackpot,” and there are enough marginalized truly wacky theories out there to obfuscate serious ones in the process.

Make no mistake, many people who’ve obtained high places in the last half-century have done so by deliberately distancing themselves from any “conspiracy theories,” the granddaddies of them all, of course, being ones concerning the Kennedy assassination.

Certainly for journalists who were eyewitnesses to the assassination in Dallas on Nov. 22, 1963, prospects for career advancement at major networks were necessarily contingent on a rejection of any “conspiracy theories.” Even PBS’s Robert McNeill, who was there and reported that he saw with his own eyes, in the confusing seconds following the shots that killed the president, police rushing up the “grassy knoll” in pursuit of something, could say only that. He’s dared not draw any conclusions but, at best, simply related only what he saw.

It is likely the Kennedy family has never accepted the “Oswald acted alone” Warren Commission conclusion. JFK’s surviving nephew, Robert F. Kennedy, Jr., seems to suggest as much in his article, “JFK’s Vision of Peace,” in the Dec. 5 edition of Rolling Stone.

The article describes how President Kennedy riled up the CIA and the war mongering right wing because he successfully negotiated a nuclear test ban treaty ratified two months before he was killed, and developed a growing resolve to get out of Vietnam. The CIA had been described as an “insubordinate, out-of-control agency” with “an unrestrained thirst for power in Vietnam.”

“Vietnam is not worth another American life,” JFK said the day before his death.