Possible, but unlikely. It's a shameful legacy that disproportionately affected minorities, but it's unlikely the original Nixon war on drugs was a direct assault on hippies and Blacks. More likely, Nixon was simply terrified of drugs [0] and overreacted and this bad policy was extended by future presidents for decades. The canard about targeting specific demographics originates with John Ehrlichman in a 2016 Harper's story [1]. Ehrichman had a real grudge for doing jail time for Watergate. Nixon's own drug czar, Jerome Jaffe, is somewhat of a pioneer in non-retributive, therapeutic treatments [2].
[0] http://www.pbs.org/wgbh/pages/frontline/shows/drugs/intervie...
[1] https://harpers.org/archive/2016/04/legalize-it-all/
[2] https://mashable.com/article/nixon-war-on-drugs#uqUHc3dQzuqZ