As an example, the park nearest my house has a guy who comes by occasionally on some busy weekends to sell pot truffles. I'm sure he makes a modest living, but I have no worry about people getting dangerously hooked. If we were to let Coca Cola put the cocaine back in, though? Or to let 7-11 sell hash and crack, with prominent placards outside and a billion-dollar ad budget? No thanks.
My other half-serious plan is for licensing. Imagine that to be able to legally buy and take LSD, you have to take a 12-week class with practical exams where you drop acid with your instructor. I can think of no better way to remove the appealing mystique of drugs than to make kids turn up after school every Wednesday for a semester and have some teacher drone at them about mechanisms of action and key safety considerations.
Have we ever seen that play out for hard drugs, when capitalism is also allowed to work on treatment and rehab?
Most people put themselves firmly in a pro- or anti- legalization camp, but in reality there are major problems (and solved problems) with both approaches.
Fully legalize and you'll encounter this horrible scenario where big companies emerge to profit off addictions. They'll lobby governments domestically and abroad. They'll engage in all kinds of shady practices to protect their businesses, just as cigarette companies have. (the oft-proposed solution to the flawed status quo)
Don't legalize and you'll miss many opportunities to help addicts, allow the black market to continue, etc. All the things you're already familiar with. (the status quo)
It's complicated.
I generally think everyone should be allowed to do whatever they want to themselves, as long as they're not being influenced by others in a way they can't control or are not fully aware of, which is what advertising and marketing generally is.
When you add in underlying physiological effects like chemical addiction to nicotine and sugar (and an ignorance of), this is clearly a case where individuals freedom and security is being infringed upon.
When the day comes that we can structure our society such that might does not make right, I'll agree with you, we should relax our laws and encourage more a more libertarian outlook. Until then, centers of power and capital need to be constrained by our legal system to protect the vulnerable.