Chuck and Lyle - well done mates, on all counts.
If he's technically competent, then shouldn't we revert to the rule which says that you're not allowed to fly if you're under the influence?
Some have alluded to the driving analogy. I don't know of too many places which ban alcoholics per se from driving, but pretty well all ban anyone from driving if they're under the influence.
If he's sober, and can control the aircraft, then what's the problem? If he falls off the wagon and turns up blotto, then just like anyone else, he can't fly that trip.
QED and consistent application of the rules.
Maybe this guy's mistake was just to not call in sick.