I've always been a skeptic, and perhaps a bit surprisingly my skepticism with regards to the Kennedy Assassination falls on the side of failing to be convinced by any of the major conspiracy theories surrounding his death. Often times it feels like folks "want" a conspiracy in order to ascribe some meaning to a meaningless (in the sense of it otherwise simply being the random act of a crazy person) event. What are the primary reasons that I should go with the "official story" of Oswald being a lucky, lone nut assassin who killed the President?
Just going to point out that the assertion that there was no cover-up and no manipulation of the Warren Commission has been disproven. The CIA admits there was a "benign coverup" by the CIA Director, John McCone.
McCone pledged full cooperation with the commission, which was led by Chief Justice Earl Warren, and testified that the CIA had no evidence to suggest that Lee Harvey Oswald, the assassin, was part of any conspiracy, foreign or domestic. In its final report, the commission came to agree with McCone’s depiction of Oswald, a former Marine and self-proclaimed Marxist, as a delusional lone wolf.
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Half a century after JFK’s death, in a once-secret report written in 2013 by the CIA’s top in-house historian and quietly declassified last fall, the spy agency acknowledges what others were convinced of long ago: that McCone and other senior CIA officials were “complicit” in keeping “incendiary” information from the Warren Commission.
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According to the report by CIA historian David Robarge, McCone, who died in 1991, was at the heart of a “benign cover-up” at the spy agency, intended to keep the commission focused on “what the Agency believed at the time was the ‘best truth’—that Lee Harvey Oswald, for as yet undetermined motives, had acted alone in killing John Kennedy.” The most important information that McCone withheld from the commission in its 1964 investigation, the report found, was the existence, for years, of CIA plots to assassinate Castro, some of which put the CIA in cahoots with the Mafia. Without this information, the commission never even knew to ask the question of whether Oswald had accomplices in Cuba or elsewhere who wanted Kennedy dead in retaliation for the Castro plots.
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While raising no question about the essential findings of the Warren Commission, including that Oswald was the gunman in Dallas, the 2013 report is important because it comes close to an official CIA acknowledgement—half a century after the fact—of impropriety in the agency’s dealings with the commission. The coverup by McCone and others may have been “benign,” in the report’s words, but it was a cover-up nonetheless, denying information to the commission that might have prompted a more aggressive investigation of Oswald’s potential Cuba ties.
So you may accept the official story if you like, but we know now that the Warren Commission was denied certain leads that could've lead to a lot more information about who else may have been involved and why. We also know that those leads didn't point to people like George HW Bush or the like, which kind of disproves those conspiracy theories hinged on that. The missing leads pointed to A) the Mafia and B) Cuban Communists. Certainly there are those out there who try to tie HW to the Mafia, but this is entirely unfounded. Makes for interesting stories though.
Here's the declassified document which this Politico article is based on.
The best book I've read that systematically debunks the various JFK conspiracy theories is Case Closed by Gerald Posner.
In addition to all the points Posner makes I would add two more:
the idea that two shooters a quarter of a mile or more apart, communicating with at best walkie-talkies, could simultaneously hit a target the size of a human head within a fraction of a second of each other is virtually impossible.
the idea that a secret on the scale of a presidential assassination conspiracy could be kept secret in Washington DC through nine successive administrations is equally unlikely.