Constructing valid arguments regarding legalization

Every now and then, I hear a common argument (from someone who partially supports drug policy reform) that goes something like this:

I agree that marijuana should be legalized — it’s really less harmful than many legal substances. But I’m convinced that harder drugs like cocaine are really dangerous and harmful to people, so they should remain illegal.

It’s a fairly common (and superficially understandable) viewpoint — at one time, I was even close to thinking this myself.
But here’s the problem. It is a valid argument only if:

1. Criminalization can be shown to reduce the harm of a particular drug. AND
2. There are no negative side-effects of prohibition.

Now there are many out there that automatically assume that A is true — they’ve heard from the government time and time again that some population group over some period of time has experienced a reduction in use, which is assumed to be credited to prohibition. But those of us in drug policy reform who have seen more of the data and analyzed the dynamics realize that it isn’t that easy.

• There’s very little evidence to show that prohibition can actually be shown to cause overall reduction in drug use over time.
• Merely reducing drug use doesn’t mean that you reduce drug harm. If you reduce casual non-problematic drug use without addressing harmful abuse, then even if you reduce drug use, you’re not fixing anything.
• Prohibition may actually increase drug use through the forbidden fruit effect, and may increase harm through unregulated purity and safety.

And, of course, “B” is huge. The fact that prohibition has negative side-effects cannot be disputed. When considering legalization, failing to address prohibition side-effects as part of the equation completely negates the validity of the argument. You have to actually acknowledge the side effects and then somehow argue that their existence is an acceptable price to pay for the supposed decrease in drug harm that you also have to demonstrate.*
And the negative side-effects are numerous and dramatic. I don’t know that it’s possible to provide a comprehensive list, but they include:

• Increased black market profits
• Violent Crime
• Corruption
• Massive incarceration
• Destruction of families
• Damage to civil liberties
• Dysfunctional foreign policy
• Loss of respect for law enforcement
• Disenfranchised populations
• Racism
• … and on, and on…

When you get a chance to lay out the elements of a proper argument, it becomes completely impossible for someone to defend the view in the opening paragraph.
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Unfortunately, too often, the discussion never gets to a proper full argument, but rather gets bogged down in silly details. We’re constantly taking on the lies spread by the prohibitionists about the dangers of drugs, and seldom getting to the rest of the story.
For example: Prohibitionists say that marijuana has carcinogens (intentionally deceptive), and we have to counter with the proven fact that marijuana doesn’t cause lung cancer. We seldom can continue to the point that the discussion has little bearing on whether marijuana should be illegal.
Sometimes I wonder if prohibitionists purposely lie, just to derail the argument.
Seriously.
If they told the truth: “Heavy use of marijuana over time can cause bronchitis.” then we could respond: “Yes, that’s true. And it’s no reason to make marijuana illegal, and have to deal with all the other problems of prohibition.”
But instead, they say something outrageous, which we don’t dare let ride, and we have a much more complex answer to get across: “No, marijuana doesn’t cause lung cancer and here’s the proof, but even if it did cause lung cancer, it still wouldn’t be a reason to make marijuana illegal and deal with all the other problems of prohibition… And it just becomes too complex and defensive for a sound-bite, so we never get out of the argument over the specific claim.
Even worse — just try taking apart the absolute nightmare of convoluted nonsensical non-logic that makes up this piece of dreck. Every part of Walter’s putrescence is intended to derail any intelligent argument.
Fortunately, more people every day are starting to see through the deception (just read through all the comments on the linked piece). But we need to take every opportunity to educate people as to what constitutes a valid discussion.
And “drugs are harmful, therefore they should remain illegal” is not a valid discussion.
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*Note: I realize that there’s also the valid libertarian argument (with which I agree) that says that it doesn’t matter even if criminalization significantly decreases harm without any side effects — criminalization still wouldn’t be a legitimate imposition on the rights of free citizens. It is unnecessary to consider this point in the context of constructing a proper argument regarding the efficacy of criminalization in reducing harm.