Conjecture: A is not the culprit because motive xyz does not check out.

Reasoning: That doesn't exonerate A, who could have other motives.

Without agreeing with it, that looks perfectly well reasoned to me.

Compelling evidence exonerating the CIA you say? Well ok, I'll believe that when I see it, just like any other evidence from gravity onward. The CIA's docs haven't been declassified and released.

Assassinating a popular, progressive president in the 1960s was very doable and didn't take a lot of people to pull off. It will never be settled as to the true motive of the killing.

Compare this to "the moon landing was faked" or "9/11 towers were not only an inside job, but imploded" and they are much less plausible.

People DO conspire. History is filled with examples both large and small. Suspecting a group of people of conspiring is not scary, there are lots of crazy theories out there that do no harm, ancient aliens, crystal skulls, all kinds of stuff.

"conspiracy theory" is a term with a lot of power, I would argue that people in power who actually do conspire have a pretty good incentive to call things that might expose them by that term. This ensures that the media cannot cover the topic without hurting their own reputation and that people who discuss it will be in the out-group and less likely to be taken seriously. In fact, they also have an incentive to play up the craziest ones (pizzagate, birds aren't real) to discredit and cover what might actually be a real case of conspiring.

You cannot stop people from coming up with crazy theories and talking to each other about them, particularly in the age of the Internet. The only thing you can do is discuss and provide evidence against them. Using that label only emboldens believers nowadays, since they become more convinced that the powerful are using the power of the term to suppress them.

In this case, history dictates that my Bayesian priors should be strongly shifted towards at least some "conspiracy" at play considering the how other leaders have been killed in the past by some conspiracy. History also dictates specifically that the CIA is capable of similar conspiracies (although this would probably be the biggest/most dramatic). The facts paint a pretty clear picture of how the assassination actually happened, but an entirely unclear picture of the motivations. Other tidbits of information strengthen and weaken these prior understandings (in my opinion they strengthen overall), but since they are only vague tidbits, the shift in understanding is small.

I believe you call this "unsubstantiated" because you do not allow history to form a prior understanding of the dynamics at play. You also seem reticent to allow for fuzzy truths or uncertainties to exist. This is entirely incongruous to the way I, and many other folks on HN, perceive the world, hence the disagreement. There fundamentally is a bottomless pit of possibilities of what happened, but this is the method in which I and many other narrow down that pit to vague likelihoods.

This seems untrue in the current media landscape. It is more likely people will disagree and then drift back to their echo chamber.

Unfortunately this isn't limited to conspiracy theories. We spent the better part of the years with leaders and scientists forcing similarly baseless explanations down or throat rather than taking the time to collect the data that actually supported the politically favorable talking points. There were countless fantasies made up to explain the risks of the specific virus, efficacy of masks, net benefit of vaccination, etc.