In the time of King Benjamin, for example:
there were many holy men in the land, and they did speak the word of God with power and with authority; and they did use much sharpness because of the stiffneckedness of the people (Words of Mormon 1:17)
Lehi tells his sons, Laman and Lemuel:
And ye have murmured because he [Nephi] hath been plain unto you. Ye say that he hath used sharpness; ye say that he hath been angry with you; but behold, his sharpness was the sharpness of the power of the word of God, which was in him; and that which ye call anger was the truth, according to that which is in God, which he could not restrain, manifesting boldly concerning your iniquities. (2 Nephi 1:26)So sharpness is a synonym for plain and can be mistaken for being angry. It is also associate with the power of the word of God.
Mormon laments:
Behold, I am laboring with them continually; and when I speak the word of God with sharpness they tremble and anger against me; and when I use no sharpness they harden their hearts against it; wherefore, I fear lest the Spirit of the Lord hath ceased striving with them. (Moroni 9:4)While sharpness might be mistaken for anger, among the wicked it causes anger. Speaking the word of God plainly is hard for them to take, as the Book of Mormon amply demonstrates.