Coca has a purpose, both traditionally and also medically, and shouldn't be suppressed. The War on Drugs does have to end, and along with it any form of drug prohibition, but even besides that, coca should never be suppressed. It's just a way for us to try to control countries that grow it.
"Inviolable" is the wrong word. "Futile" is more apt. Attempting to stop coca production is an exercise in futility. The war on drugs has been a colossal failure. This plant has been used for centuries, and there is enough of a market around the world that there will always be a buyer, regardless of price. Trying to stop this plant's cultivation is a fool's errand. It is a waste of money and resources that could be much better spent.