Despite the fact that some 'medicine' causes a ton of harm. Gotcha. Treatment for benzo withdrawal is expensive to society and can cause problems in the medical industry as addicts make up fake prescriptions.
There are hundreds of drugs. Legal and illegal is one way they're classified. This classification has a ton of determining factors. One that is overlooked is lobbying by drug companies. Another is politically motivated, or racism. Marijuana was considered a 'black' drug. Hashish was considered an Arab drug. Opium, and the derivatives were considered Asian drugs. Cocaine was originally a South American indigenous drug. Alcohol, of course is the white man's drug.
Drug companies are often accused of creating a disease to suit the drug that they develop.
Hence we have situations like the drug Atenolol which is used to treat blood pressure having the same net effect as a clove of garlic a day, although garlic has less side effects. Modern western medicine largely ignores Asian herbalism, Indian ayurveda, and tons of indigenous herbs all over the planet. They're, in large, puppeteers of the form of capitalism under the disguise of the pharmaceutical industry.
Viewing things in black and white is potentially harmful to the individual. My mother was addicted to Valium, had ulcers, got Alzheimer's, and passed earlier than she may have. Had a certain doctor not been the drug pusher that he was, who knows how many more years she may have had a healthy life.
I think we should be looking more closely, doing the research, allowing for individual differences, and more. The easy way out is to say if it's medicinal, it's good.