As someone with first hand experience regarding this very issue... the pilot was perfectly capable of flying the aircraft in fog, weather, etc.
However,
On paper... he was not
legally qualified to do so in this particular case.
I have flown with a number of captains who had to enter holding, and subsequently divert to an alternate because they had just recently upgraded from First officer to Captain and had not yet gained 100 hours as captain of that particular aircraft.
as a result... the minimums for an instrument approach have to be increased by a certain factor.
on paper... if he increases the minimums as the book says, and the minimums for the approach are higher than the weather is low... his hands are tied, no choice, though the captain in this scenario would have tens of thousands of hours of flight time and perhaps an even greater number of approaches in foggy weather... he has
no choice but to call up dispatch on the horn, coordinate with them, go to the alternate, or return to the hub.
plain and simple.
the pilot's choice of words were poor... he should have said something like
"Ladies and gentlemen, i apologize for the inconvenience but the foggy weather at our destination airport has dropped below the minimums for our approach, we will have no choice right now but to divert to __________ airport, once there we will either wait out the weather and resume the flight, or wait for the company to make a command decision for re-booking you folks on another flight at a later time."
this would be the point in time to ding the flight attendant and let her know whats up so she can answer the flood of questions that are sure to fire at her.
funny story, but the problem is there are going to be 8 out of 10 people who dont understand the context of "not qualified to land the plane" and freak out about "what sort of people are the airlines hiring these days?!"
poor choice of words on the part of the pilot and perhaps irresponsible reporting on the part of the media