The denial of the coming Messiah had long been a feature of Nephite apostasy. It was considered the most telling of all the markers of one who had left the Nephite religion. One might continue to follow the law of Moses, but if they rejected the coming Messiah, they rejected a fundamental principle of the Nephite religion.
The people at this time clearly continue that denial, a denial made more ironic in that they were very close to the signs of Christ’s birth.