If drug addicts do not reproduce at a lower rate than non-addicts, and if this equality persists from generation to generation indefinitely so that the average addict has exactly as many great-great-great-great grandchildren as the average non-addict, then we need to seriously rethink the idea that drug addiction is harmful to the addict.
Harm is a concept that best applies to a living creature. A rock can hardly be harmed. Break a rock in half, and you have two rocks, but there's nothing about the rock that makes this count as a harm. Living creatures can be harmed. What makes something count as a harm in a living creature is that it interferes with biological function. But something is a biological function only if it increases the probability of survival and reproduction (and survival matters only because it is necessary for reproduction - so, in the final analysis, what matters is reproduction). Therefore a harm to a living creature, being something that interferes with biological function, necessarily reduces its probability of reproduction. The flip side of this is that if something does not reduce the probability of reproduction, then it is not a harm.
And if drug addicts are not actually harmed by their addiction, then we must seriously question our intuitions about what is and what is not harm. If they look awful, if they look sick, if they look like walking death, and yet if they reproduce just as robustly as the rest of us, have just as many kids, grandkids, great grand kids, etc, then we need to seriously question our intuition that drugs harm the addict. Once we've done that, then we need to seriously question our specific intuition that getting "hooked by superstimuli and stuff" is as harmful as it looks.
However, I actually think we don't need to seriously question any such things because I really don't think that drug addicts are unharmed by drugs.
What we want for ourselves and our descendants is obviously not (or at least no longer) the same a reproductive fitness. The obvious example is contraception. It seems plausible that given environmental factors such as contraception and the modern welfare state that drug addicts might produce at an above average rate. That the human race might perpetuate under these conditions is no reason to rejoice about a future in which humanity is made up of crack-heads.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
If continuing the discussion becomes impractical, that means you win at open threads; a celebratory top-level post on the topic is traditional.