Rhetorical: Alma’s next device is to argue from the other side of the descendants of Lehi. Where the Nephites enjoy the privileged side, the Lamanites are obviously available as the bad example. This tells us that while the Ammonihahites did not consider themselves as necessarily wholly Nephite (witnessed by their rejection of Alma as the religious representative of Nephite culture, while maintaining some king of political position vis a vis Zarahemla), they do not consider themselves Lamanite.
Wherever the influences came from that lead to the florescence of the order of Nehor, it is not considered a Lamanite source, else Alma’s argument here will have little impact. Alma is counting on the cultural dislike of the Lamanites by those who are culturally Nephite.
Alma begins the argument by simply introducing the Lamanites, and presumably an accepted understanding of them, that they are cut off from the presence of God. For Alma’s argument to have weight, the Ammonihahites must accept this assertion implicitly. Once again this suggests that the Ammonihahites do consider themselves Nephite in some sense of the word (certainly more political than religious, but the cultural definitions of the people would be difficult to segment into neatly separate pieces).