That's not how heroin or addiction or exploitation work.
Many people have received single doses of heroin or its analogs. The vast majority of them are not addicts.
I have multiple junkie friends who decided to stop buying and using opiates.
Ultimately the choice is the user's, and nobody's attitudes or beliefs can change that simple fact. It's actually a GOOD thing that the buck stops there, and not anywhere else.
It's not anyone else's place to decide for someone that their addiction is or is not detrimental to them. I am addicted to caffeine and while many (eg Mormons) might call that a bad thing, I vastly prefer my life addicted to caffeine over my life when I am not.
The world would be a much better place if free heroin were available in unlimited quantity on every streetcorner.