Unofficial writings of our prophets and apostles provide us with a great deal of valuable information. There are a very, very few teachings which are accepted by the LDS people as true, even though they have not been officially canonized. These are probably accepted because common sense dictates that they are logically, when viewed in conjunction with doctrines that are official. The belief in a Mother in Heaven is one of these. We believe, as the Bible teaches, that we are literally sons and daughters of God and that He is the Father of our spirits. If this is the case, then it follows that we would also have a Mother in Heaven.
See, you are making my case for me. We dont mean the same thing by the words used here. In Christianity, being Gods children doesnt mean there is a mother goddess whos married to God the Father and they produce spirit children. Instead, it is speaking of adoption (Romans 8). Also, being perfect (Matt. 5:48) does not mean becoming a god, but loving all people as God does. It is clear when you read the context of Matt. 5:43-48. Also, when Christians speak of God, they mean a single being called God, not one of three gods in the godhead. They dont mean a god who used to be a man on another world and has a goddess wife. The beliefs are radically different.
I can't help but wonder why you are so interested in those things that are not official doctrine. Wouldn't it make more sense for you to question us on things that are official doctrine and that we really do teach, week after week, month after month, year after year?
Well, mostly because these things you term as "not official doctrine," come from the mouths of your own prophets.
"Hence, the doctrine of a plurality of Gods is as prominent in the Bible as any other doctrine. It is all over the face of the Bible . . . Paul says there are Gods many and Lords many . . . but to us there is but one God--that is pertaining to us; and he is in all and through all" (Joseph Smith, History of the Church, Vol. 6, page 474). "In the beginning, the head of the Gods called a council of the Gods; and they came together and concocted a plan to create the world and people it." (Joseph Smith, Journal of Discourses, Vol. 6, p. 5).
"God himself was once as we are now, and is an exalted Man, and sits enthroned in yonder heavens...I say, if you were to see him to-day, you would see him like a man in form -- like yourselves, in all the person, image, and very form as a man....it is necessary that we should understand the character and being of God, and how he came to be so; for I am going to tell you how God came to be God. We have imagined and supposed that God was God from all eternity, I will refute that idea, and will take away and do away the veil, so that you may see....and that he was once a man like us; yea, that God himself the Father of us all, dwelt on an earth the same as Jesus Christ himself did." (Joseph Smith, Journal of Discourses, Vol. 6, p. 3).
Whether you recognize these statements as truth is beyond me, but your "prophet" sure did. Am I wrong?