The social segregation of the dissenters is made clear here. They "were a separate people." This is where the irony of Alma's churches becomes clear.
While the churches provided a tighter community of believers inside of a larger community, they also allowed for a very clear and obvious distinction between the members and the non-members. Prior to the institution of the church in Nephite society, religion occurred on a community level, and the individual participation could be overlooked. Once there were institutions that declared specific allegiances, the dissenters were more individually obvious. This polarization would tend to increase the cohesiveness is almost the same way as the churches would have increased the cohesiveness of the believers.
Mormon's conclusion that the dissenters remained separate "ever after" is somewhat problematic in that he will embark upon the specific stories of some who did not remain separate "ever after."
Why does Mormon appear to give us a statement of pessimistic finality, and then immediately contradict it? The answer is that there are some exceptions, and the Alma the Younger and the sons of Mosiah are the most important of those exceptions, but the general trend was to create a division in Nephite society on religious lines, and that this religious division and tension would remain with Nephite society "ever after." Indeed, it is quite likely that Mormon was witnessing first hand some of the same problems created by the Nephite apostasy in his own days.
“And They Were a Separate People As to Their Faith”
Verse 2 is fascinating because it highlights the essential nature of many of the most serious apostasies from the Nephite faith.
The issue is never one of the nature of ritual purity for sacrifice such as many of the theological discussions in the Old World became. While the absolute dividing lines among Sadducees, Pharisees, and Essense are not at all clear, the substance of some of the points of issue are better known. All of those differences come from differences in interpretations and applications of the law of Moses. None of them deal with the denial of an atoning Messiah.
The New World was unique both in its advanced knowledge and understanding of the mission of the atoning Messiah, but also in the tremendous religious and social divisions that belief caused in their society. The essential apostasy of Noah and his priests lay in the rejection of the atoning Messiah, which (and we have seen) formed the substance of Abinadi's preaching. Abinadi preached the atoning Messiah specifically because the priests had denied that message.
Here we have the very same rejection of this doctrine arising in Zarahemla, only a short generation after all those who were actively fighting against that idea had defected to the Lamanites (see Words of Mormon 1:14-16).
Thus, even inside Benjamin's society that had been drawn together as one people in a powerful experience, there is still something that is leading the younger children away - those children who could not rely upon their personal transformation to support their adoption of the covenant and name that Benjamin confers upon them.
This situation requires more examination. While it is true that the opportunity for innovation exists in any human society, the fact is that change occurs less frequently when those societies exist in a vacuum. The study of cultural change is a complex topic, and there are certainly multiple factors in any change. It is understood that while change does occur at the level of individuals, there are factors that come from a larger perspective that enable that change in the individual that eventually spreads to the group (Barnett, H.G. Innovation: The Basis of Cultural Change. McGraw-Hill Book Company, 1953, p. 39).
The particular type of change witnessed here is one that is a substantial undermining of basic common belief structures of an entire community. We have an entire adult population with a particular belief structure that they are surely passing on to their children. In the ancient world, the role of religion as the very definition of reality was so strong as to be nearly absolute. This conception of the power of religion was so strong that when a cultural group was defeated by another group, the reason for the defeat was often given as the superiority of the god (and therefore religion) of the other group.
What is therefore most fascinating in verse 2 is that the children of very committed parents are discarding a fundamental belief so rapidly, and in reasonably large numbers. That should not happen in a closed society. The change might occur, but one would not expect it to occur that rapidly. Barnett suggests:
Barnett is describing something very similar to what we have here. This is clearly an unwanted change from the perspective of all of the adults who remain committed not only to their covenant of name (name of Christ) but also to their experience (which the children could not remember - indicating that the adults clearly did). From where does such unwanted change come?
Barnett does suggest that it is possible to come from the inside, but suggests that there are also influences from the outside.
With what kind of change are we dealing with the Zarahemlaite religion? Was the change internal or external? The internal change does not seem very likely. The children would have been taught by their parents the religion that the parents adopted. With no outside influences, we would have to suppose that some individual inside that group of children was a religious innovator, and a sufficiently important person for his (her?) ideas to become popular with peers even though they were opposed to their parents.
While that situation is still a possibility, the fact that this is the very same heresy that occurred in Noah's case, and the one suggested by Sherem even earlier, indicates that this is a tension that has gone on for some time - for hundreds of years. What the children are doing is not innovating, but copying. This copying perforce must come from outside of their social group, because the dominant beliefs of the group were different - and unitedly different. This dissention indicates a continued contact with some group outside of Zarahemla who did not adhere to the covenant of Benjamin.
The last interesting part of the passage comes in verse 3. Because of their denial of the coming mission of the atoning Messiah, "they could not understand the word of God; and their hearts were hardened." This rejection of a specific tenant of Nephite religion led them to a rejection of the entire "word of God." In other words, they rejected not only the mission of the atoning Messiah, but virtually all of the religious of their fathers. What we have in the children is a rejection of the religion of their fathers.
Once again, the connection between religion and the understanding of reality cannot be emphasized to heavily for the ancient world. By rejecting their parent's religion, they also rejected a fundamental definition of the way the world worked. That had to be replaced somehow, and the best explanation is that they adopted a religion from somewhere else.
As with other religious conflicts in the Book of Mormon, this one appears to heavily rely upon the existence of a competing religion that was prevalent in the world around the Nephites. The prevalence of that "other" religion also appears to be one of statistical domination, since the very same influences appear in Nephi as well as in Zarahemla.
The Mesoamerican setting for the Book of Mormon suggests precisely this type of religious domination by a competing religious philosophy. The threads of Mesoamerican thought can be traced from the Olmec through the Maya and later to the Aztecs (though more significantly modified by the Aztecs). Into a world filled with such a consistent but diametrically opposed world view we set the Book of Mormon peoples. In such conditions it is not surprising that there are so many apostasies from Nephite religion.