Alcohol can be nasty stuff, ruining health and lives. I have never enjoyed imbibing it myself; I can sip a little bit of white wine without grimacing, but I'd rather be having fruit juice, and that's about my limit. However, this isn't out of some morality of temperance. I have no objection to those who use alcohol responsibly.
This is a specific instance of a more general ethical principle: you should have the right to do anything you like to precisely the extent to which it does not infringe on the rights of others. (A good ethical principle, but barely a start to building an ethos; the set of circumstances in which your prosecution of a right does not conflict in any way with anyone else's rights comprise so tiny a minority of situations as to be nearly pathologically irrelevant.)
So why is alcohol different than other "controlled substances"? Obviously for nothing but historical reasons. Is there a logical reason why alcohol should be treated differently than marijuana, or cocaine, or LSD? I posit that one principle can apply to all of these. To wit: As long as you can use a substance without endangering, harming, or infringing on the freedoms or rights of anyone else, and you do so informedly, there's no reason you can't use it. The minute you break any of those rules, you should not be allowed anymore.
Imagine if it worked like this. To get an "alcohol license", you are required to demonstrate knowledge of alcohol (similar to a driver's license for driving): how it works, how to use it safely, what warning signs to watch for, how to avoid harming those around you through its use. Do this through a test administered by your local government, with private businesses offering classes to prepare you for it. A fee is charged for the license, which covers the cost of administration and enforcement, as well as ongoing educational programs and assistance programs for helping people curtail alcohol use. The license must be renewed every two years with a "bumper" test, smaller than the full test, just to make sure you're still informed and keeping current.
If at any time you are caught in any alcohol-related violation, your license will be suspended or revoked. This would include providing alcohol to unlicensed persons, driving under the influence, participating in any illegal activity under the influence, or anything else that could be linked back to alcohol use. Those whose alcohol licenses are revoked have a minimum period they can't get another one, which increases with number of suspensions, after which they need to start over with the test. A second revocation is permanent. Note that any crimes committed under the influence are still tried the same as without alcohol, in addition to the revocation of the license; including vehicular manslaughter.
Finally, medical treatments covered by state-subsidized or socialized medicine would not include coverage for damage that can be conclusively linked to alcohol use. Private insurers would be able to offer plans that did or did not cover alcohol-related costs at their discretion, with no obligation to provide an alcohol-inclusive plan to anyone at any particular price beyond existing controls on their pricing. In other words, any medical costs you incur through the use of alcohol are your problem too, whether that be through paying more (a lot more, probably!) for insurance that covers alcohol, or through not having insurance cover it.
If this would work, why not the same for marijuana? Marijuana is, by most accounts, far less likely to cause harm to self or others than is alcohol, after all. But why stop there? If you can use LSD safely and without harming others, why not have an LSD licensure system?
The fly in the ointment is the question of addiction. Why not go the next step and offer cocaine and heroin licenses? There is an assumption that it is possible to use alcohol without addiction, perhaps also marijuana, maybe even LSD, but not cocaine or heroin. Therefore, we tend to assume that cocaine or heroin cannot be made safe even with a licensure system. However, I'm not so sure. Not to get loony-libertarian here, but if cocaine were available legally and easily, but with licensure, would the depradations of cocaine be so bad? If you could get a certain amount regularly, by safe, legal, and relatively inexpensive means, would you risk losing your license to get a bit more by dangerous, illegal, and expensive black market contacts? Is it possible to have cocaine as a regular habit without the need constantly increasing, given safe, regular, and legal supplies?
I don't know. I don't even drink beer, and have never experimented with any mind-altering substances more potent than Jimi Hendrix albums. I don't really have the medical knowledge to judge such things. But even if the answer is no, it doesn't change the underlying principle. Saying "this substance cannot be safely used because it inevitably leads its user to a situation of using it unsafely" does not change the validity of an ethics based on allowing the use of substances that can be safely used. The distinction between what can and can't be used safely should be made based on medical science -- an understanding of the chemistry of addiction, of biological effects, etc. -- and the resulting conclusions about controllability. Not based on tradition or history, let alone arbitrary moralities with no basis in physical fact.