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.