There are too many unknowns in the scenario, Hudson, and the important thing is TO STOP QUICKLY using all available means. If the warning was false or the fire contained within the cowlings etc etc and the a/c went nastily off the end or an evacuation was delayed by a slower stop, then it would probably have been better to use reverse. Also it is only 'on' for a short while.
I do not have to hand the details of the MAN 737 accident to which you refer, but I could not see how any criticism could be levelled there - how would the crew know exactly what had happened? There was an example where no reverse would have delayed the evacuation. The only 'operating' criticism which I recall was on another aspect of the BA Airtours SOPs which the Captain followed - and were subsequently changed..