What do you suspect?
For shits and giggles, let's compare apples to apples. Desoxyn (Methamphetamine HCl). There you get the scary M word, but one that's FDA-approved and prescribed--though, admittedly, not commonly--by doctors. Same chemical substance minus the crystallized form, impurities, and of course, the world of illicit meth.
Oddly enough, Abbott Pharmaceuticals isn't synthesizing Desoxyn in their backyard meth lab ala shake-and-bake and Walgreen's isn't hawking it from the saddle bag of their pharmacists' motorcycles. Same substance, different context.
If you want to argue against possible long-term effects of d-amphetamine on developing children, do so. You certainly won't be alone, though for all the hysterics and despite thousands of long-term studies on its effects, there's a rather glaring dearth of support for that position. But, hey, "methamphetamine!"
They are very similar in pharmacology, so you'd be deluded to not compare the two. Same addictive properties, same deleterious effects on health, similar abuse potential.
In other words, your argument is inherently simplistic and purposely misleading. Despite similarities in structure, the pharmacodynamics differences between therapeutic usage of Adderall and illicit meth are significant. When you gloss over the differences, you're radically undermining your position. My point with Desoxyn, which you completely ignored, rebuts your position even more clearly.
Most medications have the potential for hazardous effects higher up the dose-response curve. That potential, however, doesn't magically negate clinical effects lower on the curve. A little is good, a lot (or with acetaminophen for instance, a little more) can be deadly. That's nothing new. Just as with potential for side effects, you and your doctor work to manage it during treatment.
On another note, when you raise the specter of crystal meth usage, you aren't just isolating it to matters of pharmacology. Especially when you're talking about usage externalities and societal benefits: the external costs associated with manufacture and distribution all come along as mental baggage with the words "crystal meth." Your hysterics purposely ignore this in order to make the comparison seem more damning on a purely emotional level.
Most people don't really realize what Adderall is, and American society as a whole seems to assume that doctors and pharmaceutical companies know what they are doing and are trustworthy, despite many indications to the contrary.
The pharmacology of "illicit meth" is no different than the pharmacology of legal methamphetamine, other than some contamination. The pharmacology of dextroamphetamine is not so different either, mainly it comes on slightly more slowly and lasts less time.
The reason that crystal meth usage is so bad for society is because the drug is truly terrible for you. I am well aware of everything you said, and I disagree that "just a little bit of amphetamines" is helpful for kids to be receiving for ADD.
I'm confident that history will see me out on this. If you want to give your children speed, have fun.
This logic could also be used to argue that acetaminophen / ibuprofen should be Schedule I narcotics since taking a dose 30x - 50x larger than the therapeutic dose would almost certainly result in death.
I disagree with your comparison of acetaminophen and amphetamines. It seems to be based on your deluded idea about dosage, but other than that, the drugs differ in some rather significant ways such as abuse potential, habituation, psychoactivity, and so forth.
You can disagree with my comparison if you'd like, but the fact remains. Don't take my word for it - I encourage you to read some of the research out there surrounding therapeutic methamphetamine as well as the more common levo/detroamphetamine.
Amphetamines are highly addictive. They require perpetually higher doses to maintain the same activity in the body, like most other highly addictive substances. I'm sure there are some legitimate therapeutic usages for these drugs (narcolepsy). However, I see them as massively over prescribed to people who do not actually require them.