How does something like a glass of wine *not* alter your concious state? At the least, it will cause a mild warmth and feeling of relaxation. What you're saying is that a person can drink but not binge, and that is true of anything. There have been plenty of times where I have seen a person take one hit off a joint and then refrain from any further smoking- and they certainly didn't turn into the characters from reefer madness after that.
I'll preface the following with the statement that I have used absolutely no drugs in over five years, with the exception of the occasional couple of beers or a glass of wine now and then, usually in social situations.
I, like a lot of folks (if they're being honest) experimented with a number of drugs between the ages of 18-22. Nothing hard like heroin or cocaine, but I smoked my fair share of pot and even used LSD and mushrooms a couple of times. And I've seen plenty of other folks using far harder drugs on more than a few occasions. While you're right that they're used to change a person's mental state, there are all sorts of mental states that different substances cause in different people. I've never felt or seen any level of agression associated with marijuana- but I know damn well that if I even look at tequila sideways, I'm going to be picking a fight (so I don't drink it- ever.) A guy on LSD can freak out and cause himself or others a lot of harm, but a person who ate some funny mushrooms is likely to just sit under a tree and giggle. A meth addict will age twenty years in six weeks and become mentally retarded and loose their teeth before they die, and a cocaine user will steal from his own mother to get a fix (sometimes- not always.)
So here's my theory, for what it's worth. I'm young enough to have been through a D.A.R.E. anti-drug program in school. It was a joke to everyone in the class, and was more of an education in identifying drugs than anything else. But one thing it did do was very clearly equate marijuana and mild hallucinogenics with harder and more addictive substances like injected heroin and cocaine. I know- for a fact, that many of the people I knew growing up who developed addictions to hard drugs later in life felt like they had been lied to by everyone about drugs generally. A lot of them fell into trying pot, and when they found that it didn't do anything particularly frightening to them, they assumed (incorrectly) that everything they had been told about all drugs had been incorrect to the same degree- so they tried one or several of the others, and ended up with a monkey on their back.
If they (the government and educational system) would just stop the nonsense and admit that smoking a joint won't turn a person into a raving lunatic who is going to steal and kill to get his next fix, but is rather less dangerous than drinking alcohol, they'd gain a whole lot more credibility about the drugs that are *truly* dangerous, and that alone would go a long way towards reducing the drug problem.