The divisiveness within Zarahemla increased to the point of conflict. The conflict was in the form of persecution. The previous story Mormon included told of the division that Mosiah made between decisions involving the state and those involving the church. Where the issues were internal to the church, Alma was the one to resolve them.
That division meant that there was an even larger divide among the people. There was no pretense at religious unity, and those who were not of the church were increasing in numbers, and becoming more open about their dislike of those in the church. Mormon tells the story only in terms of church and non-church, but the nature of the Zarahemla society and future events strongly suggest that there is an implicit division between those who came from the land of Nephi and those who had already been in the land of Zarahemla. Both this religious divide, and the future issues over kingship, are most logically to have generally followed that Nephite and Zarahemlaite division.
Because this was no longer internal to the church, but an issue that affected the whole community with its potential to divide, it became an issue for King Mosiah. Mosiah therefore declares that there should be no persecution. While this certainly protected the church believers, it also served as an attempt to remove an issue that could increase the divisions among Mosiah’s people.