That LBJ theory was out in Texas before JFK's body eas cold. I was in Austin that day, and before the Univ ersity of Texas closed that day, I had already heard that Johnson was in a different, closed car behind the President. An "older" Texan questioned me about what I had heard, and I repeated what I "knew". The man nodded knowingly and said words to the effect that that bastard Johnson had arranged the murder. So well thought of was LBJ.
Of course, you are correct that publishing a book that pandered to that theory was dishonest at best, as zero evidence points to it, indeed, all physical evidence points to Lee Oswald and the "Fair Play for Cuba Comm.." which consisted of.....LEE Oswald.
So, as noted, the fruit does not drop far from the tree. HOPE he gets caught in a "process crime" .