2 Behold, we have not come out to battle against you that we might shed your blood for power; neither do we desire to bring any one to the yoke of bondage. But this is the very cause for which ye have come against us; yea, and ye are angry with us because of our religion.

3 But now, ye behold that the Lord is with us; and ye behold that he has delivered you into our hands. And now I would that ye should understand that this is done unto us because of our religion and our faith in Christ. And now ye see that ye cannot destroy this our faith.

4 Now ye see that this is the true faith of God; yea, ye see that God will support, and keep, and preserve us, so long as we are faithful unto him, and unto our faith, and our religion; and never will the Lord suffer that we shall be destroyed except we should fall into transgression and deny our faith.
Moroni is doing a few things with this speech which are perhaps under appreciated.

 Most significantly, he was refuting the Lamanite Casus Belli or justification for war. The Lamanities had been stirred on by the Amalekites and Zoramites who likely portrayed the Nephites as unjustified aggressors. The Zoramites had likely described the Nephites as a hostile power that stood ready to invade and destroy their way of life. Moroni wanted to make it clear that he and his people did not want to conquer but merely to defend.

Also, by linking their faith in God to their victory, Moroni hoped that he could motivate at least some of the Lamanites to think deeply about the rightness of their cause. We already saw with King Lamoni that the Lamanites (and Nephites) strongly ascribed defeat to divine disfavor. So Moroni hoped to make these men doubt the rightness of their cause and conduct. He hoped to lead to conversion, but if not conversion than at least desertion. He hoped to demoralize his foe and therefore gain a victory.

We see later in the chapter that this was at least somewhat successfully. Many abandon their arms and walk away peacefully. But others including their commander are deeply caught up in their vision of Nephite craftiness and wickedness that they are willing to fight to sure death rather than surrender.