I'm curious as to why "man" is pluralized in that title of that History Channel program. Was it really completely about the idea that LBJ was responsible for the assassination or was it just throwing that out as a possible theory?
It was a conspiracy between the CIA and LBJ to rid Washington DC of all the Kennedys. LBJ hated both Kennedys and LBJ had deep ties to the military industry in the US. JFK did NOT want to ratchet up Vietnam but LBJ had already promised his business cronies a boost in business. LBJ has a long history of playing dirty politics. If you don't believe me look at his record in Texas. Another good one is Sirhan Sirhan....yeah he acted alone.
This is a left-wing looney theory that has been out there for a long time, the idea that JFK intended to pull out of Vietnam (which conveniently exonerates the liberal patron saint of the heinous Vietnam crime in which he had a strong hand) but that the military industry wouldn't have it because of the great profits they saw coming from Vietnam, so they had him killed. This is not a theory that is usually advanced by conservatives.
I don't deny that LBJ was a dirty poltician - as dirty as they come. I also don't deny that there was some kind of conspiracy behind the Kennedy assassinations (John and Robert) and the King assassination. But I don't think that anything as vast as what you were talking about could have been kept secret for 40 years.
I think Kennedy would have won re-election comfortably in 1964 had he run, and he would not have pulled out of Vietnam as the liberals have convinced themselves. He would have ended up in the same mess as LBJ, though he may have done it a little better.
Republicans did not push through the civil rights laws of the 1960s, but a larger number of Republicans than Democrats supported those laws, since the Democrats at that time were effectively two parties - a more progressive northern wing and a backward southern wing. Republicans provided the margins of victory for those laws.