Paul is over simplifying drug use. There is really no such thing as non violent offenders.
First consider all of the violence committed to bring the drugs to the streets. Now consider all of the violence that occurs in the streets such as gangs killing each other to control the drug sales in that area.
Now the person who purchases the drugs may not have committed a violent crime, but he is the cause of the violence that has been committed to bring the drugs to him.
So was everyone who took a drink during Prohibition a violent offender?