We learn two important lessons from these verses, one spiritual and one historical. The spiritual lesson follows form Alma’s example in the exercise of his mission to Ammonihah. Even though he finds resistance, he pleads with God “in might prayer” to find a way to reach the people. However, he clearly does not stop at prayer, and still make still makes the attempt to teach them, else they would not be able to provide the very specific rejection that Mormon lists.
The historical lesson deals with the nature of the political and religious alliances of Zarahemla. Clearly Ammonihah recognizes the authority of Zarahemla over it. They reject Alma because he has no political authority over them. While they are aware of his religious authority, they feel no need to heed that authority as the do not recognize it. The separation of Nephite religion from the political structure is complete, and sufficiently separate that Ammonihah can proclaim political dependence while rejecting the religious dependence.