There are various points made about this 'grey' area of decision making. The thread start question was "you HAD an indication of a fire…" From this I assume the cargo fire extinguisher was fired and the fire light went out. All the comments about evacuation or disembarkation seem to assume there is still a fire. Why do they assume this? Take care, of course, but what do you really expect? In the case of earlier generation types of B737, DC9, MDXX's etc. there was no fire detection or extinguishent. The hold design was such that it burnt itself out without fuselage damage, in theory. You would pull onto stand none the wiser.
Now there is some indication and it would be prudent, if the warning was out, to alert the fire boys and have them standing by for the cargo hold opening. But again, what do you expect? If the fire warning is out, and the hold is designed to burn the O2 to suffocation without damage, which = 2 kinds of extinguishent, why not believe it? OK, there are those who believe it is always a case of hope for the best and plan for the worst. In some cases, true, but it would be debilitating if applied to many aspects of life. It would be an interesting court case to chuck all the pax out, have injury claims because they claimed there was no need and it was a panic measure. What would the defence be? A lawyers field day. Ask 100 captains and get 200 opinions.