Culture: Verse 28 describes Nephites who are still Christians but who have departed from the pure gospel. Verse 29 records the rise of non-Christian alternatives. They not only deny the Atoning Messiah (like the Nehors who have been the bane of Nephite religion throughout its history) but also persecute genuine Christians.
Obviously, they are more heavily influenced by the outside pagan world and were probably geographically far removed from Bountiful, which would have remained a sphere of Christian influence. More distant points would have retained the older religions, and it is logical that they reasserted themselves in Nephite culture at this time.
Religion and politics were tightly interwoven. (See commentary accompanying Jacob 6:9.)
What Mormon sees as religious persecution might be interpreted as political stress from a historian’s perspective. Mormon is telling us of pressures focused against traditional Nephite culture, especially toward its most characteristic institution: the church of Christ. This statement becomes the foreshadowing of all-out war.