While 50% of those who occupied our White House this century were capable of having innocent Americans killed to advance their careers, I suspect the percentage in the previous century was dramatically less. That level of evil is extremely rare. I despise LBJ, but the accusation is absurd.
Absurd, perhaps, when it comes to evidence. But hardly absurd in terms of the man's capabilities.
LBJ was an evil man; thoroughly amoral and quite capable of ordering the death of JFK...and anybody else who got in his way.