"Cannabis prohibition, on the other hand, has historically been targeted explicitly at minorities"
Note: targeted at minorities by minorities.
The African American community was hugely supportive of the "War on Drugs", until it became clear that it wasn't helping.
But seriously, in the 1960s through 1990s, plenty of powerful African American politicians supported the War on Drugs.
http://prisontime.org/files/2013/07/oberia-dempsey-war-on-dr... . The "War on Drugs" was built with huge support from the African American community, we Americans as a whole thought it would be good for us.
It was believed that the white man oppressed African Americans through the use of drugs. Therefore, by declaring the war on drugs, the Black man would become freer. Things didn't turn out that way :-(
Today, the "War on Drugs" is clearly not helping. Eric Holder / President Obama ordered the FBI / Justice Department to go easier against drug offenders.
So it is clear to our current leaders (as well as African American leaders) that we need to end the "War on Drugs".