One might wonder, Why did Mormon have to write on infant baptism? And why did Moroni choose to include these writings in the abridgment? Critics of the Book of Mormon have generally focused forward in time and linked Mormon's epistle on infant baptism with the practices of infant baptism associated with the Catholic Church. They have also credited the inclusion of a discussion on infant baptism to be a spinoff from the religious debate associated with Joseph Smith's boyhood environment.
However, according to Thomas Cherrington, the inclusion of material on infant baptism could have had something to do with Jaredite tradition--a tradition that led to their confusion on the role of Christ, and ultimately became a sign of their rejection and destruction.
We find the following in the Joseph Smith Translation of the Bible:
And it came to pass, that Abram fell on his face, and called upon the name of the Lord.
And God talked with him, saying, My people have gone astray from my precepts, and have not kept mine ordinances, which I gave unto their fathers;
And they have not observed mine anointing, and the burial, or baptism wherewith I commanded them;
But have turned from the commandment, and taken unto themselves the washing of children, and the blood of sprinkling;
And have said that the blood of the righteous Abel was shed for sins; and have not known wherein they are accountable before me. (JST Genesis 17:3-7)
In other words, the descendants of Shem at the time of Abraham (and perhaps the people at the time of the brother of Jared would be included here) had lost sight of the significance of baptism and the role of the Savior. Not only were they sprinkling infants at baptism, but the symbolism of the baptism was directed to Abel (or the blood of Abel). If such practices or traditions had been passed down through the Jaredite generations, this might explain Moroni's choice to include this bit of Nephite history along with his inclusion of the Jaredite record. If such was the case, this might explain the basis of universal salvation in the Jaredite-Mulekite Nehor doctrine. The Nehors believed that "all mankind should be saved at the last day, and that they need not fear nor tremble, but that they might lift up their heads and rejoice; for the Lord had created all men, and had also redeemed all men; and, in the end, all men should have eternal life" (Alma 1:4). Perhaps the Nehors believed the Lord had "redeemed all men" because Abel's blood had balanced the scales for man after Adam's "mistake."
Thus, in his choice to insert the material on infant baptism, perhaps Moroni was primarily focusing backward in time (rather than forward), and giving the reader just one more parallel on a pathway to destruction shared by two great covenant nations--the Nephites and the Jaredites. [Thomas Cherrington, Personal Communication]