That's what we're doing. And it's also what the abolitionists did in pre-Civil War days regarding slavery, at risk of life and limb.
But consider this: the Constitution has protections against cruel and unusual punishment. Incarceration for drug possession, IMHO, violates that dictum. I'm sorry, but subjecting a non-violent person whose only offense is possession of an "unapproved" substance to the Darwinian, "law of the jungle" conditions that exist in modern prisons is cruel and unusual. If the prison system was reformed to strictly separate sociopathic homosexual rapists from non-sociopaths who would prefer not to be sexually violated and harshly punish those who commit prison rape, then I might not feel quite as adamant about the "cruel and unusual" aspect of incarceration. I believe that the corrections establishment prefers to keep this environment of terror in place because it makes their jobs less complicated.