In all fairness, he addressed that by saying some constituent parts of MJ have shown great promise for medical issues, but smoking the leaf is not necessary to obtain that.
"Until a nonsmoked rapid-onset cannabinoid drug delivery system becomes available, we acknowledge that there is no clear alternative for people suffering from chronic conditions that might be relieved by smoking marijuana, such as pain or AIDS wasting." - Marijuana and Medicine: Assessing the Science Base (1999), Institute of Medicine
Prior to federal government stopping hemp production through the misapplication of the Marijuana Tax Act, cannabis was prescribed for a variety of maladies. It was not smoked, but prepared as a tincture by soaking in grain alcohol.