Fair point on the slippery slope.
On the racism bit, racial motivation is of course not a "disjunct" as you earlier said. It is entirely relevant because it whips up a populace and a legislative body to treat the issue unscientifically, with a resounding cultural impact. We know that cannabis is way misclassified in its drug category. Why is that? We know it and many other (but not all) drugs were criminalized on moral grounds, which is not scientific at all. It increases its degree of illegality beyond what is consistent and reasonable.
We have a very detailed and strong historical grasp of race in this country. We can trace the primary historical agents in this country's fiber to just a small handful of themes, and racism is one of the big ones. We will never have "100% proof!" that it was banned on purely racist grounds, because that would literally require "hi, I'm banning weed because I am a racist and hate black people, and will play on white America's discomfort with Mexicans to achieve it". No, instead we have to cross reference the views, intent, and consequences of those promoting and supporting the ban. If we can philosophize or intuit good semantic categories of interpretation, we can run meaningful and rigorous analysis and come up with definitive evidence that racism played a strong role in the banning of cannabis. We can construct an empirical narrative, can run regression models, and can examine all kinds of primary and secondary source material to make confident claims. My non-expert education in this issue tells me that such analysis has already been done and came to such conclusions.
This is not to say that cannabis is banned purely out of racism. Hardly so. It is also a threat to Fordist modes of production, but not a threat to the modes of production that came before Fordism (and right on time, its ban), nor after. The problem is, like wages and prices, laws are "sticky".
There is also people, both users and observers who have observed it to be harmful. There are also those who postulate logically why, though their premises may (and I believe are) wildly off so their logic comes to false conclusions. There are those who have a total fear of the concept of drugs in general and will do everything they can to rationalize it. There are those who have a strict principles of how a society should look and feel and think that cannabis is an anathema.
Each one of those things is worth a discussion. Little of that is scientific or consistent with the logic of why certain things are legal, illegal, or otherwise. It just so happens that all of those things contribute to its status. I'll wrap up this point in the next two paragraphs. And on to my song's bridge before the final chorus!:
You'll notice the least harmful drugs, (hallucinogens, MDMA, and the hardest of the softest drugs, cannabis) are the most illegal. The most physically and socially damaging ones like alcohol, cocaine, methamphetamine (with heroine not fitting the trend) are much less illegal. Which ones interfere with rote modes of production? Hint, the stimulants push you deeper into the system, not away from it.
So what's the point? The point is, we are stacking reasons to ban and restrict this drug that are motivated by forces that are not in accordance to our highest values of science, liberty, sound philosophy, and equality unto the law. We could have a consistent drug policy that banned drugs for consistent proportional reasons--which is something you more or less articulate (you call for more restrictions on legal things). But we don't, and given what's legal--caffeine, alcohol, nicotine, aspirin, others--and given why those things are legal from a non-corrupt standpoint, cannabis is irrationally and severely mischaracterized. Enough science is in, and that science says to fix our legal discrepancy, we need to ease, if not eliminate, restrictions.
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And you are right, it doesn't meet the standards required of drug manufacturers, but for the opposite reason. It is way more regulated and prohibited in research than the chemicals the pharmaceuticals are playing with. So it could never even go through that very stringent process. AKA, of course it doesn't meet standards, because it gets special treatment of having already amazingly higher standards.
Many of the other illegal drugs with demonstrated medicinal use value are either just as questionably illegal (again, LSD, MDMA), or much shown to be *seriously* harmful in certain common-enough cases but are actually prescribed by doctors in certain circumstances (cocaine, heroine, and methamphetamine). And those less illegal, more harmful ones have clear and much more legal and somewhat less harmful prescription analogues (methylphenidate, morphine, dextroamphetamine).
P.S. I like that you don't quote war. Makes for a much better discussion.