In addition to any personal vendetta Amulon had with Alma, there was a very clear religious chasm between the two. Amulon had (with others) put Abinadi to death, and Alma had taken Abinadi to heart. That difference alone might have been sufficient to create this command from Amulon. He exercises his authority to limit the expression of the religion of Alma's people, a religion with which he had disagreed before, and now had even more reason to hate. This command is an extension of the same reasons Amulon increased the tribute burdens upon Alma's people.