Rhetoric: Alma rises to a rhetorical climax here by openly accusing some in his congregation of following Satan, not Yahweh-Messiah. Undoubtedly, he does not accuse every person listening to him of this state, but it suggests that their numbers were large enough to warrant both Alma’s resignation from the judgeship and this very pointed sermon.
Alma’s “proof” of his contention is that their denials of following Satan indicate that they are “liar[s] and [children]… of the devil.” How can this be true?
A common human trait is self-preservation through rationalization. We make ourselves believe that our actions are acceptable, even when they are not. Those who had been pierced in their hearts would admit their sins and begin repenting. But those who continued to deny their wrong-doing were continuing to deceive themselves. They would not repent and thus would find themselves aligned with Satan at the last day.