Aren't there many studies that prove the opposite of what he said? Maybe supply/reference those?
Still hasn't been one death with marijuana as the only drug in their system, correct? How many deaths from tobacco?
Pretty outrageous.
I'm not sure if he'll take it seriously or not (or if he really believes what he wrote), but I would definitely approach it from an objective point of view and not that of a toker.
Good luck.
