“So I got up and Humphrey was absolutely distraught, he was just absolutely beside himself with anxiety and concern. And we then received a telephone call from Steve Smith and Pierre Salinger in California. They said, ‘There's a brain surgeon we trust in Boston. Could you arrange for a private plane to fly him to Los Angeles? Because Robert Kennedy's still alive and there's a possibility of saving him.’
Humphrey called up the commanding general of the air force, who happened to be there at the academy. And Humphrey said, ‘Will you please dispatch this plane?’ The general said, "I surely will."
“Ten minutes later we received a call from an aide in the White House: President Johnson had canceled the plane because Humphrey had no authority to send it. The fact was, Johnson preferred Robert Kennedy dead.
“It was one of the most heinous acts I've ever experienced in my life, and it all but broke Humphrey's heart.” [C. David Heymann, RFK: A Candid Biography Of Robert F. Kennedy, p. 505]
--Ted Van Dyk, Aide to then Vice President Hubert H. Humphrey
Valenti knew what a liar LBJ was as well as a "mean bully" who "could humiliate you, both publicly and privately."
The idea of investigating the new president LBJ, whose every private utterance concerning Robert Kennedy was a death threat, or the CIA in the JFK assassination was verboten - off the table - even before the Warren Commission was created.
I think we know why Bill Moyers has not written his memoirs of working with Lyndon Johnson.