That is the most ignorant statement I have ever heard. A world without drugs aside from killing everyone on medication, myself included, would be the most boring place ever.
First of all you have to stop relating things like heroine and marijuana. Although they are both drugs they are in no way the same.
With that being said, I happen to agree that there are some drugs the world could do without.
1. Anti depressants - EDIT: In the big picture perhaps a necessary evil.
2. Oxycodon - This is an opiate derivative that is EXTREMELY addictive and is probably the most abused drug today. If you can avoid this painkiller I would reccommend doing so.
3. Meth Amphetamines - "Crystal Meth" is an epidemic in our nation and is totally useless except for the purposes of getting high but at the risks of chemical dependence and severe damage to the body. This is not a natural drug, but a synthetic combination of chemicals. This could go as well.
Some good drugs which btw are all naturally occurring substances:
1. THC "Marijuana" - Treats multiple illnesses, chronic pains, and stress. And it can be grown in your closet or backyard. Does not kill brain cells, does not impair motor functions, is not addictive, and has NEVER caused any fatalities. The reason this drug is illegal is because of hemp.
2. LSD - See Aldous Huxley's Doors of Perception, this drug is very neat on the brain, and contrary to superstition, does not remain in your spinal column. The dual nature of the DNA double helix molecule was discovered by scientists on an LSD experience.
3. Psilocybin - The chemical in mushrooms, civilizations since recorded history have all used this drug in religious ceremonies and spiritual gatherings and healing rituals. And it truly is a great experience. There is a species of mushroom that if you mistake for "magic mushrooms" can kill you, so educate yourself on which mushrooms are ripe for picking. I reccommend the documentary, "Know your mushrooms" for psilocybin lovers and anyone who likes botany and plants.
4. Cocaine - Actually has more medicinal effects than marijuana. But the black market commercial form has many additives they use to cut it with and a high susceptibility to addiction.
www.Erowid.com great source of information on all drugs
All drugs must be considered responsibly and scientifically as they all have some kind of effect on the body. But they are not our enemy, they are merely tools.