In mid-1831, Ezra Booth, a strong advocate and missionary, left the church after concluding it was false. He subsequently wrote a series of nine letters to a Methodist minister friend, detailing his departure. These letters are among the earliest and most insightful accounts from someone directly associated with Joseph Smith who became disillusioned.
In his fourth letter, Booth described why some people remain devoted to the religion even when confronted with evidence of its falsehood. His words are as relevant today as they were when he wrote them:
“You will doubtless say, can it be possible that the minds of men, and men who possess the appearance of honesty, can be so strangely infatuated, as still to adhere to a system, after it had occasioned so much agitation, and so much disappointment. One reason which can be assigned for this, is, the adherents are generally inclined to consider the system so perfect, as to admit of no suspicion; and the confusion and disappointment, are attributed to some other cause. Another, and principal reason is, delusion always effects the mind with a species of delirium, and this delirium arises in a degree proportionate to the magnitude of the delusion. These men, upon other subjects, will converse like other men; but when their favorite system is brought into view, its inconsistencies and contradictions are resolved into inexplicable mystery; and this will not only apply to the delusions now under consideration, but in my view, to every delusion, from the highest to the lowest; and it matters not whether it carries the stamp of popularity or its opposite.”
Ezra Booth, Letters (Ohio: September 1831).
http://www.truthnet.org/Mormon/Mormonismunveiled/15_1831Ezrabooth.htm