A heavily smoking gun to which believers in a conspiracy cover-up point is a memorandum, written by deputy attorney general Nicholas Katzenbach, on Nov. 25, 1963, to LBJ aide Bill Moyers. It read, in part, “(T)he public must be satisfied that Oswald was the assassin; (and) that he did not have confederates who are still at large.” It also recommended that “speculation” or “hearings of the wrong sort” be headed off. Four days later, Attorney General Robert Kennedy and Katzenbach recommended a seven-man committee – the future Warren Commission – investigate the case.
Both Douglass and Salandria quote the “satisfaction” sentence as proof the commission was created to sell the public the Oswald-bill of goods, and prevent the truth of the NSS conspiracy from being discovered. Talbot, who also quotes this language, takes a more nuanced view. He is favorably disposed toward Katzenbach because he would (a) state a belief that the FBI and CIA hid facts from the committee and (b) allowed that someone besides Oswald might have been involved. (Katzenbach believed that Oswald fired the only shots but might have been backed by others. His bet was on anti-Castro Cubans. This helps Talbot’s call for the release of more records, but does nothing for the JD/VS-school which considers Katzenbach a criminal co-conspiritor.)

Significantly, neither JD, VS or DT quote the very first sentence of the memorandum: “It is important that all of the facts surrounding President Kennedy’s assassination be made public.” Nor do they quote its call to have “a complete and thorough FBI report on Oswald and the assassination” made public as quickly as possible. Katzenbach would testify to the HSAC that he had wanted all the facts on the table. If, as the FBI was saying, Oswald acted alone, that case had to be made. If Oswald was part of a conspiracy, left or right, that case had to be made. The public worldwide had to know “the true facts had been revealed…”
Now you don’t have to believe Katzenbach, but it seems at least intellectually dishonest for the conspiracists to quote selectively in order to hide an interpretation counter to their own from being arrived at. Of course, if it wasn’t hidden, the conspiracists would have had to explain why the not-yet-created committee would decide to follow a “satisfy-the-public-with-Oswald” directive rather than an “all-the-facts” one.
Additionally if, as JD?VS believe, the NSS had falsely marketed Oswald a Marxist Kennedy-killer in order to inflame public opinion sufficiently to justify an invasion of Cuba and/or nuking of the USSR, why would it want a commission to cut off speculation that the Red Menace was at work? Or was there a second peacenik conspiracy, including the FBI and Lyndon Johnson, trying to stymie the CIA/Joint Chiefs/industrialist one? (Douglass seems to suggest something like this, At one point he has J. Edgar Hoover telling Pres. Johnson that the CIA had “doctored evidence” linking Oswald with the Soviets. Johnson seeking to avoid “global war” did not take the CIA-dangled bait, but he also elected to avoid confronting the CIA, hoping equally to avoid “a war within the U.S. government.”)