It is difficult for me to write about the drug war, not because I feel less passionately about it than other pressing matters, but because I feel so passionately that it is pure unadulterated evil.
An exaggeration? Here's a reminder of the kind of horror  the drug war brings to the lives of innocents.
As others have said, it is not drug addiction, but drug war addiction, that afflicts the United States. A solid majority of Americans are complete and total drug war addicts, and, like all addicts, are paranoid and defensive at the slightest mention that their addiction might be causing harm rather than good.
The practical arguments against the drug war are overwhelming. It has never been shown to have prevented a single person who wants to use drugs from purchasing and using drugs. It has made criminals fabulously wealthy. It has resulted in the corruption of countless government officials. It never has, and never can, succeed, but it can, and does, cost billions of dollars and God knows how many lives.
Practical considerations alone provide plenty of reasons for opposing the drug war. And yet the moral reasons for opposing it are even stronger, in my opinion.
Let us review some basics in the contract between citizens and government.  Governments are instituted among men to provide order where there might otherwise be chaos, to provide for defense against outside aggressors, to adjudicate crimes, and to settle contract disputes.
Governments are NOT created to run the lives of citizens down to the last minutiae. They are NOT created to persecute innocent subsets of the population. No, not even when a democratic majority vote to do so.
Where is the line drawn between legitimate government action and illegitimate intrusion into the lives of free men and women? To the drug war addict, drugs are bad, bad, BAD, so bad that anything is justified, even raiding a Santa Cruz (California) cooperative which served only dying people who worked the land themselves, and who used marijuana as a relief of last resort for their symptoms.
Other drug war addicts say, no, that was a mistake, but we need to persecute (sorry, I mean prosecute) "recreational users" while sparing anyone who can prove he/she uses drugs for a valid medical reason. A new bureaucracy will be created to classify citizens as to who may, and who may not, use a particular drug.
Think about this. An adult human being is to be made to apply for permission in order to put something into his own body. I would argue that such a decision is more basic, more fundamental, even than the right to speak one's mind freely.
Am I saying that everyone should start taking drugs? No. That such a thing would happen without the drug war is a paranoid fantasy of the drug war addict. There are drug abusers with the drug war, and there will be drug abusers after the drug war ends. People who are not writing a self-destructive script for their lives avoid drugs, or use them carefully. People who are writing another script do seem to find a way to do so, laws or no laws.
Am I saying, conversely, that "treatment on demand" should replace punishment for drug use? Again, certainly not! It is not the responsibility of Joe Taxpayer to pay for Johnny Badtrip's treatment in a posh facility. Johnny needs to fall as low as he decides to, then pull himself out, if he chooses to, when he chooses to.
Am I saying that drug use does not negatively impact "society?" No. Any act of any sort may negatively impact someone or something. Suicide, for example, has a terrible impact upon those who are left behind. And yet suicide is a basic right for a free human being. It is monstrous and obscene to force someone who wants to die to live just for the pleasure of others.
(Persuasion is of course both moral and desirable. Hats off to the volunteers who work suicide hotlines! Most who flirt with death really are, as the cliche has it, crying for help.)
These arguments apply also to what are now prescription drugs. It is foolish, of course, to take any drug, for any purpose, without being informed as to its applicability and its risks. Nevertheless, attempting to outlaw foolishness is both naive and pointless, not to mention expensive and immoral. Those who want to find prescription drugs in the grey market do so. Only persuasion can help others make wiser decisions.
Shame on all drug war addicts! If you want to do damage, do it with your own lives, not with the lives of others.
 I sidestep here the question of whether government is even legitimate in any form. There are many who argue persuasively that it is not, and that private contracts can better handle all aspects of life which are now handled by governments.