If there is an Elder here, or any member of this Church, called the Church of Jesus Christ of Latter-day Saints, who can bring up the first idea, the first sentence that I have delivered to the people as counsel that is wrong, I really wish they would do it; but they cannot do it, for the simple reason that I have never given counsel that is wrong; this is the reason. This people, called Latter-day Saints, have been laboring now over forty years. Forty-three years last April,...' (Journal of Discourses, Brigham young, Vol 16 pg 161)
The Journal of Brigham's Discourses were highly regarded and transcribed directly from his own secretary. The Journal of Discourses was given to, verified, edited and approved by Brigham personally and it seems with much care (as Joseph also edited the history of the church). Their standard works do not have to match what they teach, as most all of the LDS doctrines are not found in the Book of Mormon or Bible. You have to understand they do supplement their daily readings of scripture only with 'approved' LDS books, and then deny these are influential or standard books.
Understand that a Christian can be so by trusting just scripture. It is not necessary to put faith in any man or organization. This is not true with Mormonism, you must believe Joseph was a true Prophet. The whole Mormon conception and idea is that the truth was lost, and they have reintroduced prophets to the church, which will restore the things which were lost. Thus the Mormons teach that 'many plain and precious things' were removed and lost from the bible. So you must trust them to restore the truth of the bible, and these two men Joseph and Brigham were the two who developed the Mormon teachings. So you are told to put your trust in these two men, or put your trust in Gods word. To deny either of the two Prophets is to reject truth according to Mormonism.
The Journal of Discourses, History of the church, and all the other books the church now refuse to admit as doctrinal show the true nature and history of these two supposed prophets. It is not so much only about their doctrine, but 'who' these two were and 'how' they lived. We can see that they ruled as dictators using threats of divine punishment against even their own family members and friends. Both highly charismatic, they boasted of themselves and their supposed intellect, insulted all who would disagree, manipulated and controlled their environment. They both gained much money and power, and of course each had multiple multiple wives, including very young girls. And at the end of the day their doctrines teach the exact opposite of scripture, and are found no where in actual church history.
So the question is: Do you trust God has kept His Word like God said He would, or do you trust Brigham and Joseph?
'It is better to take refuge in the LORD Than to trust in man. It is better to take refuge in the LORD Than to trust in princes' (Psalm 118:8)
'Thus said Jehovah: Cursed is the man who doth trust in man, And hath made flesh his arm' (Jeremiah 17:5)
'The grass withers, the flower fades, But the word of our God stands forever' (Isaiah 48:8)
'But the word of the Lord endures forever." And this is the word that was preached to you' (1Peter 1:25)
'For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished' (Matt 5:18)
'Heaven and earth will pass away, but My words will not pass away" (Matt 24:35)