From your article....
"Those selling small amounts of drugs to support their own drug use may go to jail for decades."
So, by selling small amounts, they are violating the law. To go to jail for decades, it would have to be habitual offenses.
Drugs destroy families and communities, that is why there are laws against possessing and selling them. If you look at all crimes, there is a similar comparison to the offense rate of drug offenses across the races quoted in the article.