The prisoners are given a choice, just as were the prisoners of Moroni. They could honorably accept either alternative, although one alternative meant death or some other means of certain punishment. In both cases the honor of the men dictated that they could only accept salvation if they actually could accept the conditions of the salvation. They could not lie and be saved.
In an odd moral for our personal journey, the same choice is given to us. We, just as the prisoners, are given two alternatives, a way of life and a way of death. Even though our moral position might be tempted to lie to temporarily accept the way of life, the lesson here is that it cannot be done. We truly receive the way of life only if it works its way into our hearts. We cannot lie our way into salvation.