John Ehrlichman, former Chief Domestic Advisor to Richard Nixon, in 1994 on the motivations for the war on drugs:
The Nixon campaign in 1968, and the Nixon White House after that, had two enemies: the antiwar left and black people. You understand what I’m saying? We knew we couldn’t make it illegal to be either against the war or black, but by getting the public to associate the hippies with marijuana and blacks with heroin, and then criminalizing both heavily, we could disrupt those communities.
We could arrest their leaders, raid their homes, break up their meetings and vilify them night after night on the evening news. Did we know we were lying about the drugs? Of course we did.
You start out in 1954 by saying, “Nigger, nigger, nigger.” By 1968 you can’t say “nigger”—that hurts you, backfires. So you say stuff like, uh, forced busing, states’ rights, and all that stuff, and you’re getting so abstract. Now, you’re talking about cutting taxes, and all these things you’re talking about are totally economic things and a byproduct of them is, blacks get hurt worse than whites.…
You can listen to the full conversation this quote was taken from here.