First, when people involved in addiction treatment say that drugs cause people serious problems aside from legal issues related to the drug itself, I wonder if they are biased by only seeing the users who hooked badly enough to land themselves in various sorts of rehab/therapy programs. Do we know how many people are using these drugs in a more casual way, suffering little to no real harm from them, and never coming to the attention of the legal system?
Second, you say below in reference to heroin being dangerous how many people die of overdoses every year. I was under the impression that the reason overdoses are so common is that, since it is illegal, there is no regulation or easy way to determine the purity of any given batch of it, so it is easy to accidentally overdose if you get a stronger batch than you're used to. If opioids are really that fundamentally dangerous, why is long-term monitored use of methadone etc not considered to be a bad thing, as opposed to going cold-turkey ASAP?