The very fact that Amlici is willing to consider military action suggests that there were a significant number of people in his community. This also reinforces the need to remove themselves from within Nephite society, as a military action requires a support base.
Following Sorenson's suggestion, this separate community would have existed prior to this time, and the removal noted in the text would have been of those supporters who did not already live in the separate city.
In the proposed setting, both the physical separation and the connections to the Maya lands ("Lamanite" at this point in Book of Mormon history) would have supported the adoption of Mesoamerican culture, including kingship and its Mesoamerican trappings. At this time in the history of Mesoamerica, wars were increasing. Some of the fighting was territorial, and some was religious. In all of these facets, the Amlicites are fitting well into the known Mesoamerican patterns of the time.