Odale, I understand your argument, it's not a gateway drug because it is illegal. Legalizing it will not change the physiological effect it has on the body, nor will it change physical effect it has on it. The funny thing with drugs, especially with mood altering ones, is that you slowly become addicted to them the more you use them and their effect on the body diminishes over time.
Every two pack a day smoker started with a single cigarette. When one cigarette once in awhile is no longer enough, it becomes one more often, and so on and so on and so on and all of a sudden you are at two packs a day. The fact that cigarettes are legal hasn't changed this quality.
The thing with dope is that its affects are much stronger then nicotine or alcohol. The body becomes more dependent on the THC quicker for its effects. Eventually, even 3 or 4 or 10 joints a day won't do it and before long, you are into the stuff that can kill you on your first dose. Legalizing it will not change this property.
Does every dope smoker become a cocaine addict? No. But nearly every cocaine addict started with dope.
The thing is, people like the high these drugs induce. So much so that even if they can't get it, they make it with what ever they can find under the sink. Meth, crack etc..etc..etc.. Legalizing or decriminalizing some of these drugs is not going to change this real problem either.
I don't know what the answer is. Looking at how they treat alcohol might be a start. Yeah, there are people who, because of their addictive natures ruin their lives and the lives of others. Yet it is not illegal, not everybody who has a glass of win, a pint of ale or a jigger of spirits does so. Is it the education society has put out? Is it that people are generally more mature about it? You can't enjoy a drink outside of a licensed establishment or within the confides of a personal residence.
Something just came to mind:
A lot of very bad people have been put away where the police where able to pick them up on drug possession charges. Is this a tool taken away? Al Capone was put away on tax evasion, it wasn't the murders he allegedly did but at least they put him away. Imagine where we would be if 5 years prior to that if society decriminalized or legalized tax evasion? Doubtful they will ever do so with tax evasion but then, 30 years ago, we were saying the same thing about the war on drugs. And here we are today, talking about it and in some states and provinces, doing it.