Lamoni is “astonish[ed]” that the explanation that is so clear to him only unleashes his father’s wrath. His own changes have been so complete that he has forgotten his own prejudice against Nephites. Lamanite tradition had taught him to hate Nephites, just as Nephite traditions had taught hatred for Lamanites. Free in the Spirit, both Ammon and Lamoni have stepped away from the false “traditions” of their fathers to meet as brothers in Yahweh-Messiah.
Lamoni’s father reminds Lamoni of what must have been a traditional argument: the Nephites have robbed Lamanite property and plan to do so again. Of what have the Lamanites been robbed? The best answer is given in Mosiah 10:12–17:
They were a wild, and ferocious, and a blood-thirsty people, believing in the tradition of their fathers, which is this—Believing that they were driven out of the land of Jerusalem because of the iniquities of their fathers, and that they were wronged in the wilderness by their brethren, and they were also wronged while crossing the sea;
And again, that they were wronged while in the land of their first inheritance, after they had crossed the sea, and all this because that Nephi was more faithful in keeping the commandments of the Lord—therefore he was favored of the Lord, for the Lord heard his prayers and answered them, and he took the lead of their journey in the wilderness.
And his brethren were wroth with him because they understood not the dealings of the Lord; they were also wroth with him upon the waters because they hardened their hearts against the Lord.
And again, they were wroth with him when they had arrived in the promised land, because they said that he had taken the ruling of the people out of their hands; and they sought to kill him.
And again, they were wroth with him because he departed into the wilderness as the Lord had commanded him, and took the records which were engraven on the plates of brass, for they said that he robbed them.
And thus they have taught their children that they should hate them, and that they should murder them, and that they should rob and plunder them, and do all they could to destroy them; therefore they have an eternal hatred towards the children of Nephi.