1. Perhaps the most powerful single piece of evidence that there was no conspiracy in the murder of President Kennedy is simply the fact that after all these years there is no credible evidence, direct or circumstantial, that any of the persons or groups suspected by conspiracy theorists
We'll call this Fallacious Bugliosi Argument 1.
The first fallacy is that absence of evidence is not evidence of absence.
The second fallacy is that "credible evidence" is lawyer rhetoric for "I'm dismissing anything that doesn't fit my preconceived conclusion".
Otherwise, all I have to say is "there is no credible evidence that Oswald killed Kennedy" and we're done.
And in the conspiracy prosecutions I have conducted, I have always been able to present direct evidence of the co-conspirators acting in concert before, during, or after the crime, and/or circumstantial evidence from which a reasonable inference of concert or meeting of the minds could be made.
Oh, you mean like several witnesses reporting having seen Ruby, Tippit, and/or Oswald together prior to November 22? Yeah, I know, that's not "credible". Because....reasons.