A consenting adult might be able to make the rational decision to do or not to do MDMA. But when someone, say, becomes addicted to heroin, their mind changes so dramatically you honestly cannot even call them "consenting adults" in the same sense anymore.
In addition, we know from alcohol prohibition that (besides failing to stop or greatly curtail usage) it tends to incentivize drug producers to push more of the hi-octane stuff because it minimizes their risk: beer was not popular during prohibition while liquor was. If opiates are generally legalized, this evidence shows that the vast majority of people who decide to use them (which is already a tiny minority) will stick with making tea rather than messing with syringes, minimizing the creation of new hardcore addicts. Many benefits come with legalizing all drugs; an exhaustive set of arguments can be found in the book Chasing the Scream by Johann Hari.
[0] See James Fadiman's studies performed in the 1960s before it all got shut down. A collection of these can be found in the Psychedelic Explorer's Guide.
It's not okay. It's an evil drug that kills tens of thousands of people in the USA annually, both innocents and users. If we were honest with ourselves we would take a good look at alcohol and its role in our culture/society, but we won't and will look for scapegoats to alcohol-rooted problems in other things.
> But alcohol is ok because
I think part of the bias is that when one thinks of alcohol one thinks of having a beer after work - opiates conjure up images of shooting up heroin. But a massive fraction of people take opioid pain killers on a temporary basis and suffer no ill effects - I'm sure many of them would admit that being under their influence is at least somewhat pleasant. Likewise, media seems slow to cover cases of horrific alcoholism with massive systemic organ failure. In Russia, for example, the life expectancy of men is 64 years old, largely due to a culture encouraging copious alcohol consumption.
Secondly, there are all sorts of drugs, some addicting, some not addicting, some legal in some places, some illegal in other places, some making people "irrational", some making them more "rational". There's no correllation between these attributes.
Legality depends on historical accidents more than anything. Alcohol is in fact one of the more addicting drugs out there, see the high percentage of "functioning alcoholics" out there.
That's why I said mostly rational. Out of the thousands of little decisions and behaviors we engage with in a given day, most are rationally chosen to move us towards our goal. Most are basically habit, of course, not some long, drawn-out process. But, still rational.
> There's no correllation between these attributes.
Oh, I'm not arguing that current drug policy is great and sensible. I think it should be liberalized. I just don't think a total free-for-all is a great idea either. Ideally we'd set the status of a drug -- recreationally legal vs medicinally legal vs decriminalized vs illegal -- based on its societal harm, rather than whatever ad hoc method we use right now.