Bias and conditioning? There is large and measurable variability in potency, effect, and dependency formation. Anyone with any sense sees the difference between coffee, marijuana, pcp, and heroin.
It's the dose that makes the potency and effect.
The dose available to the end-user is determined from the drug itself and the supply chain, since it is unregulated. If it were regulated, the individual doses would be more controlled, allowing for less habitual redosing, and less acute mental and physical dependency.
Imagine you want a beer but hafta volumetrically dose it from 100% grain alcohol and cider. It'd be easier to become an alcoholic. Similarly, it is harder to "responsibility" enjoy heroin/fent or coke/meth because every time I want a small amount, I have to stare at a weeks worth for a brief moment.
The illegality of drugs itself becomes tautologically entwined with the reasons they are illegal. It is becoming more difficult to diffuse as our culture leans to polarity on drug issues.
The drug prohibition made it difficult to know how many people use drugs responsibly. It is linked to legal weed actually: it is being legalized not because research showed it is not too dangerous (we knew it for a while), but because more and more people become aware that you can totally use weed and remain a respectable member of society.
For me it is a question of personal freedom. Everything has risks. Going hiking in mountains can kill you, for example, or almost any outdoor activity really. And some people die there pretty much every day. But I really don't want the state banning it just because some people fuck up.
Have I heard about diabetics refusing to change their diets and dying, yes.
Does that mean we should outlaw sugar? Probably not, plenty of people struggle with obesity and sugar is a major contributing factor, but there's plenty of responsible adults that can consume sugar in moderation.
I also imagine there are a non-zero number of people that begin using more pure forms of caffeine in ways that are damaging to their relationships, health, and careers.