The first question to be proposed by a rational being is, not what is profitable, but what is Right. Duty must be primary, prominent, most conspicuous, among the objects of human thought and pursuit. If we cast it down from its supremacy, if we inquire first for our interests and then for our duties, we shall certainly err. We can never see the Right clearly and fully, but by making it our first concern. No judgment can be just or wise, but that which is built on the conviction of the paramount worth and importance of Duty. This is the fundamental truth, the supreme law of reason; and the mind, which does not start from this in its inquiries into human affairs, is doomed to great, perhaps fatal error. The Right is the supreme good, and includes all other goods. In seeking and adhering to it, we secure our true and only happiness. All prosperity, not founded on it, is built on sand. If human affairs are controlled, as we believe, by Almighty Rectitude and Impartial Goodness, then to hope for happiness from wrong doing is as insane as to seek health and prosperity by rebelling against the laws of nature, by sowing our seed on the ocean, or making poison our common food. There is but one unfailing good; and that is, fidelity to the Everlasting Law written on the heart, and rewritten and republished in God's Word. Whoever places this faith in the everlasting law of rectitude must of course regard the question of slavery first and chiefly as a moral question. All other considerations will weigh little with him, compared with its moral character and moral influences. The following remarks, therefore, are designed to aid the reader in forming a just moral judgment of slavery. Great truths, inalienable rights, everlasting duties, these will form the chief subjects of this discussion. There are times when the assertion of great principles is the best service a man can render society. The present is a moment of bewildering excitement, when men's minds are stormed and darkened by strong passions and fierce conflicts; and also a moment of absorbing worldliness, when the moral law is made to bow to expediency, and its high and strict requirements are decried or dismissed as metaphysical abstractions, or impracticable theories. At such a season, to utter great principles without passion, and in the spirit of unfeigned and universal good-will, and to engrave them deeply and durably on men's minds, is to do more for the world, than to open mines of wealth, or to frame the most successful schemes of policy.
I will let Channing, the still-revered father of Unitarian Universalism, speak. He defended slavery and refused to let abolitionists like Frederick Douglass and William Lloyd Garrison speak in Unitarian congregations around New England. There is a lesson and a warning for all of us who believe that being 'moderate' or 'liberal' or 'Christian' immunizes us from endorsing evil.
"... the abolitionists sent forth their orators, some of them transported with fiery zeal, to sound the alarm against slavery through the land, to gather together young and old, pupils from schools, females hardly arrived at years of discretion, the ignorant, the excitable, the impetuous, and to organize these into associations for the battle against oppression. Very unhappily they preached their doctrine to the colored people, and collected these into their societies. To this mixed and excitable multitude, minute, heartrending descriptions of slavery were given in the piercing tones of passion; and slaveholders were held up as monsters of cruelty and crime. Now to this procedure I must object as unwise, as unfriendly to the spirit of Christianity, and as increasing, in a degree, the perils of the slaveholding States. Among the unenlightened, whom they so powerfully addressed, was there not reason to fear that some might feel themselves called to subvert this system of wrong, by whatever means? From the free colored people this danger was particularly to be apprehended."