With Great Power...
Powerful tools always have the potential for abuse. Take, for a moment, the phenomenon of automobiles, particularly in the United States, where they are most common. Cars (and other motorized vehicles) give the driver great power. By simply depressing a pedal, several tons of steel can be pushed forward to incredible velocities. The momentum of a car traveling at average street speeds (45mph) is sufficient to destroy buildings and knock down trees. Almost anyone driving a car down a normal street could swerve with just a flick of the wrist and kill dozens of pedestrians at a second's notice.
And yet... we continue to use these vehicles because their great power doesn't necessarily lead to abuse. The ability to propel two tons of steel over a flat surface at 65mph, in combination with a good system of roads, allows drivers to carry themselves, passengers, and cargo over great distances with minimal effort. Indeed, our society has come to depend upon that ability.
The dangers of automobile use, though great, are controlled by careful regulation. Children are not allowed to drive; anyone who wishes to operate a vehicle must practice for many months under the supervision of a registered driver, and then they must pass several tests to be granted the license to drive. Even then, they must follow strict safety guidelines, from stopping at stoplights to wearing a seatbelt. A huge portion of the police force is dedicated to enforcing these regulations, at great expense to the taxpayers.
Our society decided that the benefits of these vehicles far outweigh the potential dangers. Despite this fact, hundreds of thousands die every year on the road in vehicle accidents. Millions more are injured, sometimes gravely. Even so, the benefits are still judged to outweigh the losses.
And so it is with drugs. Drug abuse is nowhere near as dangerous, in terms of deaths and injuries, as vehicle abuse. Yet somehow this rather obvious parallel (and others we could name) doesn't seem to occur to the prohibition proponents.