Drugs don't have to have positive value to argue for them being legal.
For example, cheap distilled spirits have little or no redeeming value. But it would be more harmful to make that illegal than otherwise. Methamphetamine (Desoxyn) is used to treat obesety and ADHD, and similar treatments for ADHD have similar potential for recreational use/abuse. But the whole Drug War is so harmful, it doesn't matter if there are therapeutic or harmless recreational uses of a drug. It would be less expensive, more effective, and more compassionate to treat addicts than to continue the Drug War, even if more people became addicted.
For example, cheap distilled spirits have little or no redeeming value. But it would be more harmful to make that illegal than otherwise. Methamphetamine (Desoxyn) is used to treat obesety and ADHD, and similar treatments for ADHD have similar potential for recreational use/abuse. But the whole Drug War is so harmful, it doesn't matter if there are therapeutic or harmless recreational uses of a drug. It would be less expensive, more effective, and more compassionate to treat addicts than to continue the Drug War, even if more people became addicted.