Mormon returns to the issue of the war, and the sad way in which the war is developing. He is commenting on things that he clearly feels have gone beyond the honorable way of war. In the ancient world, war was never a pretty thing. It was always gruesome, but typically there were rules that one would follow. Mormon appears to be suggesting that the nature of warfare has changed. Indeed, previous wars had the goal of political and economic dominance. This war is a war of intended destruction. It really was different.
Particularly abhorrent to Mormon was the treatment of captive women and children. He passes on the report that has come to him that “they feed women upon the flesh of their husbands, and the children upon the flesh of their fathers.” That is abhorrent. That is beyond our understanding. It was probably hyperbole.
If we are placing the Book of Mormon in Mesoamerica, there was certainly a practice of ritual cannibalism. However, in Mesoamerica, and in virtually all known cases, cannibalism is not acceptable except within certain confines, and typically those are considered by the practitioners as sacred. Thus, we can be certain that women and children were sacrificed. That was known practice, under certain circumstances, in Mesoamerica.
Ritual cannibalism was practiced, but nothing in the practice would suggest that it was used to humiliate, which is the suggestion here. If they were actually fed the flesh of the fathers, there would have been some religious meaning behind it, even though we would not agree with the religion that would do that.