A quote that claimed "what [the drug war] was really all about" was disrupting black communities and the anti-war left.
If Ehrlichman did say that (as you pointed out, even that is disputed) it's quite absurd. The prohibition of drugs started decades before the Vietnam War or the Civil Rights movement, and it was an international effort, in response to real dangers. It's not tenable to argue that it was all about control, nor that Nixon's motives (if those were his motives) were even relevant to the passage of the CSA with only 6 opposing votes in Congress.
That said, I agree that time has shown that prohibition has failed and can be as harmful as the drugs themselves. I just think the Ehrlichman quote adds far more heat than light to the discussion.