"What is it that inspires professors of Christianity generally with a hope of salvation? It is that smooth, sophisticated influence of the devil, by which he deceives the whole world"

- Prophet Joseph Smith, Jr., Teachings of the Prophet Joseph Smith, p. 270

"...all the priests who adhere to the sectarian religions of the day with all their followers, without one exception, receive their portion with the devil and his angels."

- Prophet Joseph Smith, Jr. , The Elders Journal, v. 1, no. 4, p. 60

“Nothing less than a complete apostasy from the Christian religion would warrant the establishment of the Church of Jesus Christ of Latter-day Saints.”

- Prophet Joseph Smith, Jr., History of the Church, v. 1, p. xl

Makes a person wonder why the morg wants to become more "christian mainstream."

He said that the desire to be mainstream was not doctrinal but emotional: Everyone likes to feel included. That makes sense to me.

Of course, there's also the issue of "respectability." Some Mormons, especially in the higher ranks, appear to place a high value on being almost a caricature of the upstanding, straight-arrow American. It's got to be a little awkward to be so mainstream in every aspect but that of traditional Christianity.

"Brother Taylor has just said that the religions of the day were hatched in hell. The eggs were laid in hell, hatched on its borders, and then kicked on to the earth."

- Prophet Brigham Young, Journal of Discourses, v. 6, p. 176

"When the light came to me I saw that all the so-called Christian world was groveling in darkness."

Brigham Young, Journal of Discourses, v. 5, p. 73
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"With a regard to true theology, a more ignorant people never lived than the present so-called Christian world."

Brigham Young, Journal of Discourses, v. 8, p. 199
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"The Christian world, so-called, are heathens as to the knowledge of the salvation of God"

Brigham Young, Journal of Discourses, v. 8, p. 171

Christianity-- is a perfect pack of nonsense...the devil could not invent a better engine to spread his work than the Christianity of the nineteenth century."

Prophet John Taylor, Journal of Discourses, v. 6, p. 167
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"Where shall we look for the true order or authority of God? It cannot be found in any nation of Christendom."

John Taylor, Journal of Discourses, v. 10, p. 127
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"What! Are Christians ignorant? Yes, as ignorant of the things of God as the brute beast."

John Taylor, Journal of Discourses, v. 13, p. 225
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"What does the Christian world know about God? Nothing... Why so far as the things of God are concerned, they are the veriest fools; they know neither God nor the things of God."

John Taylor, Journal of Discourses, v. 13, p. 225

"Christians—those poor, miserable priests brother Brigham was speaking about—some of them are the biggest whoremasters there are on the earth, and at the same time preaching righteousness to the children of men. The poor devils, they could not get up here and preach an oral discourse, to save themselves from hell; they are preaching their fathers' sermons —preaching sermons that were written a hundred years before they were born. ...You may get a Methodist priest to pour water on you, or sprinkle it on you, and baptize you face foremost, or lay you down the other way, and whatever mode you please, and you will be damned with your priest.
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Heber C. Kimball, Journal of Discourses, v. 5, p. 89

the Book of Mormon remains secure, UNCHANGED and UNCHANGEABLE, ...But with the Bible it was not and is not so....it was once in the sole and exclusive care and custody of an abominable organization [Christianity], founded by the devil himself, likened prophetically unto a great whore, whose great aim and purpose was to destroy the souls of men in the name of religion. In these hands it ceased to be the book it once was."

- Apostle Bruce R. McConkie, The Joseph Smith Translation, pp. 12, 13

“Believers in the doctrines of modern Christendom will reap damnation to their souls.”

- Apostle Bruce R. McConkie, Mormon Doctrine, see pp. 45-46