In fact, it is, because if the pathway to addiction starts with overprescription, deregulation is unlikely to alter the stats: prohibition and black markets aren't gating factors.
I think we'd need more evidence of that before just assuming it. Some number of people with current addictions would not have developed a habit if they hadn't been supplied by their doctor. Sure, there are also folks out there with habits that "doctor shopped" or whatever, but we aren't talking about those.
Now, if "deregulation" as used above means "stocking next to aspirin at CVS", then sure. But that's not what's being discussed. Haven't done a study of it, but I'm pretty sure Denmark doesn't have many folks heading signing up as addicts to experiment.
You need to capture not just addicts who got started on prescriptions, but addicts who got started through the resale of overprescribed opiates from non-addicts.
Also, the demand from Oxy addicts created (or, I suppose, upgraded) a criminal network that supplies heroin. When I was growing up there weren't that many heroin addicts around, so the local independent pharmacies didn't stock it.
If you were an adventurous youth looking for a new high you would have been sold barbiturates, maybe, or benzodiazepines. Maybe speed. But today it would be heroin, and you can trace at least some of that back to oxy addicts desperate to feed their addiction after being cut off.
What is? You didn't actually argue anything. I have no idea what you're talking about. Pointing out that Oxycontin is being abused is not an argument. What is your position?