The most superficially appealing argument for drug legalization is that people should be allowed to do what they want with their own bodies, even if it ruins their lives. Except that's not true. Back on Earth, see, we live in a country that will not allow people to live with their own stupid decisions. Ann has to pay for their stupid decisions.
"We" have to "invest" in "our" future by supporting people who freely choose to inject drugs in their own bodies and then become incapable of holding jobs, obtaining housing and taking care of their children. So it's not really quite accurate to say drugs hurt no one but the user, at least until we've repealed the welfare state.
And don't give me the now-we'll-have-to-regulate-fatty-foods slippery slope argument. Precisely because you can see a difference in eating a hamburger and smoking crack means there is a huge difference between the top of the slope and the bottom -- which is why pure slippery slope arguments are always stupid. Let me just ask: Before he serves you, would you prefer that your bus driver or investment banker had consumed a hamburger, a cigarette or marijuana?
In fact, smokers and fatty-food consumers clearly benefit society through their years of tobacco- or hamburger-fueled hard work. They also undoubtedly save the taxpayers money by dying relatively swift deaths from corroded arteries or cancerous lungs. (Junk food and tobacco companies tend not to want to advertise that particular great savings to the Social Security system, but it's true.)
As Joseph Califano has pointed out, even John Stuart Mill said there were some things people could not be permitted to choose to do with their own bodies in a free society: "The principle of freedom cannot require that he should be free not to be free. It is not freedom to be allowed to alienate his freedom." Drugs enslave people.
So do cigarettes and alcohol, the drug legalizers say. Indeed, they fervently claim that alcohol and cigarettes are no better (and probably worse) than marijuana.