New England was the center of religious opposition to the war with Mexico. There, "Conscience Whigs" condemned the conflict as an immoral conspiracy to extend the slave empire. Perhaps the most passionate and eloquent antiwar opponent was Theodore Parker, minister of the Twenty-Eighth Congregational Society in Boston. Although the outbreak of hostilities was initially greeted with an outburst of patriotic fervor, Parker and other New England religious leaders denounced the war from the outset. At Boston's Faneuil Hall in May 1846, Parker accused the Polk administration of being a tool of the "Slave Power," and urged the citizens of Massachusetts to take no part in the conflict.
Ironically, while religious opponents of the war were motivated by a deep conviction regarding the immorality of slavery, they often shared with expansionists a strong belief in Anglo-American racial superiority. As a result, sympathy for the Mexican people did not feature prominently in religious discourses against the war. Parker, for example, viewed Mexicans as "a wretched people, wretched in their origin, history and character," a race destined, regardless of American policies, to "melt away as the Indians before the white man." In the end, Parker's vision for the United States, and that of many evangelicals, was that of a nation of industrious Anglo-Saxons, in which people of color played no part.