Well, needing to use a drug is already a drug problem (addiction or not).
Do insulin users have a drug problem? I think at the core of the issue is that our society generally regards psychological ailments as a personal flaw, rather than a health issue. (I’m talking generally, not about the professor from the article)
How many insulin users lose their jobs, lose their homes, turn to acquisitive crime or prostitution to fund their insulin habit?
We can talk about how many people who use heroin this happens to, and how much it's caused by current drug prohibition laws, but it's more than zero.
Decriminalisation makes a lot of sense but we need to be realistic about the harm caused to about 10% of people who become addicts.