That's not a side effect of heroin, that's a side effect of overdosing. Death is also a side effect of overdosing on acetaminophen, and alcohol. Imagine if when I went to my local wine shop they made a mistake and sold me something that was 80% abv rather than 12-14% and I drank the bottle. Or my pharmacy gave me 5g acetaminophen tablets instead of 500mg, and I took 2 of them every four hours for a few days. Or my finely ground table salt was cut with some form of rodent poison. I'd be pretty dead in those cases most likely. Most illegal substances you have absolutely no idea what you're buying or how much you're buying unless you test it yourself. Yes, word gets around but that's no use to you if you accidentally take 10x a dose, or something that is just not what you were told it was.

Legal substances also have lots of information readily available around them - if I go to my pharmacy and ask for ibuprofen, they will tell me the dosages in advance. If I go to my doctor and they put me on oxycodone, they will give me a dose that they think is safe, (and in theory, a plan to reduce my dependence on them) without judgement. If you develop an opiod addiction, your support options are much more limited.

Thing is, good heroin/morphine is almost free of side effects. Paracetamol, for example, is a lot more dangerous than heroin.

Also, Joplin took heroin AND massive quantities of alcohol on the day of her death. It will be close to saying that when someone dies in a car crash while DUI, driving is the real and unique problem here.

But the drug-war irrationality is better exposed by taking a look at weed and MDMA. Two quite safe substances (certainly more safe than alcohol), with clear medical applications, and forbidden just because some ignorant decided to put them in Schedule I. MDMA at the time of its prohibition was being used in psychotherapy with success in tens of thousands of patients [1]. Today, no medical use is recognized, and being in Schedule I (making it un-researchable), none will be. I wouldn't be too surprised that some country discover that it could be used as a treatment for depression or PTSD.

[1] https://www.amazon.com/dp/0791418189

Switzerland started a program in 1995 where they give medical grade heroin to people suffering from addiction. From the people taking part in this program, none have died from heroin overdoses or due to toxic contamination in the drug.

So heroin is actually pretty safe if used correctly.

Death comes from _mis_use, which usually stems from _mis_information ("drugs are bad, let's not talk about them").

People die when they over-dose (which more often than not happens because they don't know exactly what they're getting, or the purity of it) or mix with other substances that they shouldn't.