I know I'm just one case, but as someone who's mother got addicted to legally prescribed Fentanyl as well as other opioids as a result of her cancer treatments, and to had serve as caregiver for said mother when said drugs sent her into irrational rages and occasionally made her suicidal (she later admitted to not remembering multiple months of time from the years she was on it), the libertarian individual choice argument is particularly full of shit when it comes to these substances.
There are some things that the average human biology simply cannot handle. Making said substances illegal or regulating them such that they are impossible for the average person to get is perfectly rational and beneficial for society. Naturally treatment centers should be provided for those who manage to obtain them illegally as opposed to jail time, and that's the part we suck at. No rational person with purpose seeks out illegal opioids, it's a symptom of underlying issues and should be treated as such, not punished.
Psilocybin, Marijuana, Tobacco and Alcohol are completely different animals. And yes there are people who can't handle these, but the vast majority of the population is capable of doing so and/or the consequences are less severe when they are mishandled. You can't say that about opioids.
Same reason even in the US while I can own an AR-15, I cannot own a Patriot Missile Battery. One the average individual can be relatively trusted with, the other they cannot.
Au Contraire! Explosives are just very difficult to buy because you must go through an approval process to purchase a "destructive device" and the storage regulations, which vary widely from area to area, are (rightfully) difficult and expensive to comply with.
Maybe for you, but why should you be the arbiter of what other people do? Make it legal and tax substances to the point that the revenue offsets the potential negatives.