Most economic activities have criminal connections, because a certain amount of dishonesty is essential for success in business. Anyway, I don't think drug consumption can easily be limited by legislation. That much is true.
Although I don't think the drug trade caused the current crisis, it does involve huge amounts of money. Black market trading can't be regulated, or even monitored accurately, so it could well contribute to economic instability. That, I now remember, was his main argument.
