Dan,
The affirmative defense is very limited, and probably wouldn't apply here. Mr. McCullough, by his own admission, was not working at the time he was carrying. I don't like the result, but that is my reading of the law.
It's in Conboy's hands, and Davis is doing a good job of pushing Conboy into a corner where it would be difficult for him to pursue a misdemeanor carrying charge.
I know of one person who did carry under the affirmative defense without issue. That person was an attorney who had been threatened by the husband of a woman the attorney was representing in a divorce. There wasn't enough to charge the husband (no witnesses but the lawyer and the husband) but the county attorney at the time (several decades ago) gave the lawyer a litteral "get out of jail card" in the form of a signed letter that would be presented to the cops if he was caught carrying.