Textual: The first thing we should extract from this passage is Mormon's reason for including it. Mormon is painting a picture of a people in apostasy, from which they will be called to repentance by Abinadi. Thus for Mormon, these events serve to set up the reason why the Lord called Abinadi to come among them. Without question Abinadi is the focus of much of this account, as the detailed presentation of Abinadi before the court will attest. At this point, however, the importance is the setup for that story, and the setup necessitates our understanding of the fallen nature of Noah and his people. Their sins include the "pride of their hearts." They have achieved a victory, but ascribe it to their own strength and forget their God. Even worse, they "did delight in blood, and the shedding of the blood of their brethren…"
It is perhaps more difficult to understand this statement from Mormon, as it is hard to reconstruct what text he would be abridging that would allow him to make that statement. However, if Mormon did understand that the armies were retaliating against hamlets, he may have well understood that the "victory" was hollow because it was directed against stationary populations rather than the marauders. The "victory" was a blood payment for "crimes" against the Noahites, but possibly not directed at the specific peoples who had committed those crimes. In that analysis, Mormon could have seen that what drove them was their "delight in blood" rather than the political necessities of defense.
Social: On a social level, this passage gives us even more information. Mormon notes that the claim of the people is that: "their fifty could stand against thousands of the Lamanites." On the heels of a victory that would appear to have been conclusive, we are given to understand something about relative numbers. The Noahites are a significantly smaller population in the land than the Lamanites. This demographic reality lies behind the statement that their "fifty" could stand against "thousands." While the statement is bellicose hubris, it must reflect their perception of a reality. The Noahites were a significantly smaller population.
The second piece of information we may extract is that the people saw their military victory as a victory against a political body of the Lamanites, not just marauding bands. For whatever reason, the focus of the conflict is now changing. Where the Lamanites had come upon small groups in the field - isolated and easy targets, somehow this "victory" is now proclaimed over the whole of the Lamanites. This further suggests the concentration of the action against settlements under Lamanite political control, and will explain the escalation of the conflict into the major offensive that will see the flight of Noah and his court later.