Alma attempts to use the scriptures as the foundation for truth, but, ultimately, he understands that Korihor has undermined the ability of the scriptures to be used as the standard of truth. Therefore, Korihor is particularly dangerous. When he is “leading away the hearts of this people,” he isn’t simply preaching a different religion, but he is undermining the entire Nephite way of life.
Alma sees that there is such danger in Korihor’s words that he declares: “I am grieved because of the hardness of your heart, yea, that ye will still resist the spirit of the truth, that thy soul may be destroyed. But behold, it is better that thy soul should be lost than that thou shouldst be the means of bringing many souls down to destruction.” Alma believes that he must choose between the destruction of the Nephites or the destruction of Korihor. Alma chooses the Nephite people.
Alma gives Korihor one last chance. Alma specifically says that “if thou shalt deny again, behold God shall smite thee, that thou shalt become dumb.” Korihor will respond with, in essence, “go ahead.”