Sherem has no love for Jacob. Yet, he begins his discussion with the endearing phrase, "Brother Jacob." This is a good example of the subtle craftiness of his speech. He portrays a love for Jacob that is not there. Nevertheless, Jacob will not be fooled.
Another interesting aspect of Sherem's use of this phrase is that it suggests that the saints of the Book of Mormon referred to each other as brothers and sisters, much like the members of the Church today.