Big Pistons
It is very hard what qualifies an electrical fire in the early stages, the first unusual smell should get the pilot looking for a problem and mentaly getting into electrical power down mode......... But not an unconsidered electrical shutdown.
A few years ago I had the low volts light come on and the alternator load fall to zero along with a smell of burnt rubber, I was thinking about shutting down the electrical system but with no other indications and all the other electrical equipment functioning I just off loaded all unnecessary electrical equipment and landed normaly....... The reason for the trouble was a broken alternator belt that had come to rest on the cylinders.
It would become very quickly apparent if things were progressing from a minor problem into one that could not be contained unless drastic action was taken, I take the view that you need to be sure that he action you are taking is the correct one for the situation and not a vast over reaction that will put the aircraft in more danger than is necessary.
Of course if you are starting to get acrid smoke, erratic indications etc there is no doubt that the electrical master switch has to go off, what I don't want to see is very low time pilots shutting own electrical systems in blind panic and then making a panic approach with no flaps or stall warning system and getting it all very wrong.............and then the accident investigators find that the inital problem was a system had shorted, there was a slight burning smell, the system CB had tripped to protect the system as it should have and there was no danger of the problem escalating.