I said "no", but that applies to the rules we have today. You see, if all drugs were legalized we would have an impact on the way society works, in terms of economics and industry most of all, so it's hard to say because, well, it would be another world, so different from today that I dare not choose at all...
For instance, let's mention one of the least (?) damaging dudes, marijuana. My father-in-law is a neurologist, I know not how to go into specifics the way he did, but once I mentioned how I saw no problem with legalizing marijuana, since common cigars are legal and so damn damaging. His answer was unexpected, though he agrees that it is hypocritical, he stated that there is an inherent damage that (abusive use of) marijuana causes and that many people ignore, it has to do with brain cells in a brain area and whatnot: ultimately, it won't kill you, but it will damage your speed for processing your thoughts for good... And that's when I strated thinking about the "funny and constantly anesthetized" manner of speaking of most of my heavily pot headed friends (not the guys who'd do it once in a while, the ones who'd eat it for breakfast if they could).
My point? If everyone exaggerates on a drug that "slows you down" like pot, we would have dramatic changes in many society levels, because, well society is nothing but a pact between the people that comprise it, a pact that comes out of common sense, culture, subconscious et cetera, you guys know the deal. Those changes could be for the worse, better, or even be dramatic but still "keep things as whole the way they already are"; I don't think we would be led to a drug post-apocalypse though, I really can't believe the majority of people using heavier drugs that render you near 100% inoperative (like crack). Point is we adapt, a quick search in wikipedia and you'll see that cocaine was at a given point sold to children, it was advertised like a sort of energetic to keep keep a-buzz at work. Hell, cigarets were meant to keep you younger and was a guarantee of prettier skin, alcohol was prohibited, the world takes some wild turns. Choose your presidents but remember: it's your companies that have all the leverage...