Although the brothers’ complaints are no surprise, their attempt to boycott the work is new. Perhaps they were simply protesting working on something so difficult. Perhaps they were reluctant to move on again after their arduous journey to this abundant coastal land. But almost certainly, as Nephi sees it, they are motivated by resistance to his leadership.
Laman and Lemuel deny Nephi’s authority to require their labor because it is socially inappropriate for a younger brother to command his elder brothers, and they deny that Yahweh is inspiring him. To oppose Nephi’s leadership, they must deny that Yahweh has directed him to do so.