The following statement is taken from Ethan Smith's A Dissertation on the Prophecies Relative to the Antichrist and the Last Times; Exhibiting the Rise, Character, and Overthrow of That Terrible Power: And a Treatise on the Seven Apocalyptic Vials (Charlestown, MA: Samuel T. Armstrong, 1811), 157-159:
In short, the doctrines of the Gospel have been perverted; and the main pillars of the Christian system have been attempted to be overthrown. Yet man has a conscience; and guilty beings under its lashes dread the judgment. Who among us can dwell with devouring fire? Who can inherit everlasting burnings? These are questions not instantly disposed of. The conscience is not seared as with a hot iron at once: This is usually a work of time. And some kind of religion, in the mean time, must be had, to quiet the alarms of guilt. But to embrace the humbling doctrines of the cross; uniformly to endure the restraints, and perform the duties of the pure religion of Christ, is intolerable to the proud heart, to the ignorant and the perverse. Some substitute then must be adopted; some kind of religion invented, more consonant with the feelings of the wicked; which yet may soothe their consciences. How perfectly are such people prepared to fall a sacrifice to the wiles of some subtle imposture. They have become habituated to despise the genuine doctrines, and the regular order of Christ. And yet, not having quite reached gross Infidelity, they seem to want some religion. The fanatic preacher arrives. And there are multitudes of them at this day! He declaims against those doctrines of grace, which are most offensive to the carnal heart; and harangues upon imaginary doctrines, which are much more pleasing. He proposes a cheap and easy religion; one which allows to man much of that independence and importance, which he claims; a religion, which saves man the labor of diligently searching and comparing the word of God, and of studying his own heart. All is done both by preacher and hearer by immediate inspiration! Proselytes become at once first rate Christians; yea, fit for teachers; being admitted to a high and peculiar intimacy with God! They reach at once the top of the mount. Every passion is addressed, and wrought up to the highest pitch. These new fangled Christians are confident, dogmatical, and above the reach of salutary instruction. The regular teachers of religion are by them accounted hirelings, and ignorant of spiritual things. The improvements of such people usually are, to learn the most common cavils against the doctrines of grace. In this they often make great proficiency. And they become a prey to enthusiasm and error, of one denomination or another, according to the notions of their teachers.
Such people are in the high road to Infidelity. Their religion is no better than a dream. Their God is only a fiction; a creature of their own imagination; and no better than an idol. The essential glories of the true God are by them denied, and often with bitterness. Such fanaticism is often followed by Infidelity, at a period not far distant. The human passions are not capable of long retaining such an elevated tone. The feelings will by and by vibrate to the opposite extreme. Such characters after a series of heats and colds, become tired of their religion. Its novelty is gone. Their former attachment to it sickens to disgust. They find much plain Scripture against their tenets. Yet they will not renounce their scheme for that which is correct. They thus form a habit of perverting the word of God.
When the early Latter Day Saint movement was labeled as a 'fanaticism', this is the sort of charge meant to be evoked. Note that this description of 'fanaticism' was written nearly two decades before the official organization of the LDS Church on 6 April 1830.