It's never been more clear than it is now thanks to Fentanyl. How often do people have accidental overdoses because their beer was contaminated? Or their Adderall? Never happens, virtually inconceivable. But the majority of overdoses from illegal drugs are due to either inaccurate dosage or unknown contaminants, problems that essentially cease to exist for legal drugs.
If we are not talking about new analogs created to bypass legislation most drugs are also produced as pharmaceuticals. And those are pure enough and dosage is controlled well enough. How often do we hear that some batch is withdrawn from market?
I think pharmaceutical contamination happens. As does over the counter products, especially under-regulated stuff like vitamins and supplements.
It's just that fentanyl risk is more dramatic than those contaminants. Maybe one is "increase your risk of cancer over a couple of decades" or even "does not have intended effect" and the other is "stop your heart soon after consumption".
Agree in parts but behind this argument there is an assumption that legal drugs would cause the market for illegal drugs to collapse entirely. Has not happened with alcohol (between 14 and 23% of alcohol sold in the US is illegal).
Adderall (fake or legit) is heavily sold illegally and their lacing with Fentanyl is a massive problem already.
I think it's imperative we prevent people from dying even if our solution is imperfect. Legal sources of currently illegal drugs would save lives full stop.