The resurrected Savior explained why we should avoid disputations about points of doctrine.
For verily, verily I say unto you, he that hath the spirit of contention is not of me, but is of the devil, who is the father of contention, and he stirreth up the hearts of men to contend with anger, one with another.
A person who has the spirit of contention is not of the Savior but is of the devil. Therefore, when discussing the gospel with a friend, do not argue or contend.
Source: 3 Nephi 11:29; The Book of Mormon: Another Testament of Jesus Christ