I don't believe LBJ was any sort of sociopath either. He was just an effective politician. For many years he was among a handful of Southern democrats who precluded any federal civil rights legislation from advancing because that was in his interest when running for office in the South. When he decided to run for president, however, he realized that no southerner could win a national election tainted with a segregationist background. So he suddenly became an advocate of Civil Rights. That was mostly a political calculation to advance his own interest. He may have had some empathy for those living in the type of poverty that he grew up in - which included many poor blacks - but that was secondary to his own political agenda. And that strategy has proven wildly successful for democrats to this day since they still get 80% percent or more of the black vote. Hard to remember now but after the Civil War most blacks considered themselves to be republicans for many decades.
He certainly lied repeatedly to the public about the war, about our progress there. H.R. McMaster's book on Vietnam, "Dereliction of Duty", is pretty devastating in its indictment of LBJ and McNamara and the Joint Chiefs for their dishonesty and arrogance. He argued that LBJ was worried more about the political ramifications of the war then about the war itself; that a withdrawal would hurt him politically and set back his "Great Society" programs. And, of course, Caro documents how he got the nickname "Lying Lyndon" while in college; he didn't begin telling untruths (I always liked that word <g>) after getting into politics.
Whether that constitutes being a "sociopath" can be debated I guess.
As to civil rights: I think he was sincere about the issue, that it was a moral question for him as well as a political one. Certainly it was a mix. But the '64 act alone was sufficient to earn him accolades. But he followed that up with another act in 1968, a Voting Rights act and a Fair Housing act. All of that was painting the legacy lily. Caro documented his experiences helping poor Mexicans and how that did affect him. He was a complex person; one that, as Caro showed, could be enormously cruel and mean and nasty but also who had, I think, a real empathy to poor and black Americans.