Heroin itself isn't the problem. It's how it turns into morphine in your body. But we solved that problem by making both illegal. But what if there's a drug that turns into GHB, the so-called "date rape" drug? Well, there is. So do we outlaw the legal drug, too, now?
(Actually, the blogger notes that the substance's effects are more like alcohol's than GHB, and also points out that the former is really the "date rape" drug:
GHB is usually described as a 'date rape drug' despite the fact that it is barely used in 'date rapes', unlike alcohol, which is used in the vast majority of cases and is a much better candidate for the 'date rape drug' label.)
But that's okay because alcohol's legal.