> Otherwise, your opinion and mine are irrelevant.<
That really applies to most of the stuff we discuss: given that it all happened 200 years ago, what we think doesn't matter at all. Napoleon has long since gone before the only tribunal that has all the information and the right to judge.
I don't suppose any general of the era didn't have a few non-judicial killings on his record (outside battle, I mean) especially when commanding in areas of civil unrest. I suppose what distinguishes this case is firstly, thelarge numbers (though I don't know how many deaths it takes to be called a massacre) and secondly, the fact that the victims were prisoners of war. Probably it wouldn't have happened if they had been Europeans. In the Russian campaign prisoners were dragged along in the retreat even when there was no food for them (ref Paul Britten Austin) and when their guards got tired of minding them and shot them it was considered an outrage.