Ok. For the benefit of those not "in the know". When an exit door on an aircraft becomes unusable the Captain HAS to, by law, consult a document called the MEL (Minimum Equipment List). Within this document will be details of the procedures and actions to be applied in the event that certain parts of the aircraft are inoperative. Some inoperative items are called "no go" items which means the aircraft is AOG (Aircraft On Ground) and it cannot dispatch with passengers until fixed. Sometimes an aircraft can dispatch without pax to get back to a maintenance base.
With respect to doors, the MEL will dictate which seats have to be blocked off and the maximum number of pax that can be carried. So an overwing exit inop is not the same as a main door inop for example. From memory a main door inop on the A320 reduces the max load by about 40% and the seating in the general area (but very specific seats) is blocked off.
It is a responsibility of the Captain to make it very clear to all passengers the implications of an inop exit and again to emphasise that safety is not being compromised (by reducing the number of pax and blocking off seats). This appears to have been done on this occaision. Can't comment on the "all pax seated on one side" aspect because I don't have access to Vuelings MEL (which has to be approved by the Spanish CAA by the way).
I can understand why passengers get nervous - they don't understand and that's not their fault (I don't know anything about medical research - but I don't get criticised for that). However what they should realise is that we, as pilots, also have a vested interest in the safe operation of the aircraft! Not only from the point of view of safety but also from the point that if we knowingly break the rules we could lose our licence (livelyhood). So no right minded pilot is going to try and "fudge it" or "try and get away with it". Even though most pilots are pragmatic and goal orientated, it's too risky from a safety and professional point of view.
Hope this goes some way to explaining things.
A4
