IMHO we must NOT pi$$ about with a fire warning.
Get the aircraft on the ground, then get the hell out. Yes, pax will most likely be injured in the evacuation, but they will be alive, not cooked. Fire in the aircraft is probably our most severe emergency - get the pax out ASAP, then argue the toss from a safe distance.
If you, Captain, made the wrong call, you erred on the side of safety and in any fair system will never be sanctioned for it.
At the end of the day, we are here to ensure pax safety and even if the airline gives the crew a hard time, they will be able to sleep nights knowing that their motive was correct.
Is anyone really brave (foolish?) enough to count on a fire warning being false???