Laman and Lemuel might have conveniently forgotten by what power they had been brought to this point, but Nephi has not forgotten. Nephi also understands that the hand of the Lord was not just on the making of the ship, but also upon the waters, and Nephi fears that the actions of Laman and Lemuel and their families should call down upon them the Lord's wrath. This may indicate that the "rudeness" also contained rudeness to the Lord, a disrespecting of his power.
In their anger Laman and Lemuel rekindle their hatred of Nephi for his usurpation of what they felt was their birthright - the leadership of the family. When Nephi warns them of the impending wrath of the Lord, they do not hear the warning, but instead hear the lecture. They do not hear the concern for their welfare, but rather they presumption of a younger brother counseling his elders. Their fire of their anger is fanned.