He wrote constantly for the newspapers and became well-known for his literary interests, but he found a more popular subject in temperance reform, which he took up with characteristic assertiveness. From 1830 till the approach of the Civil War he spoke and wrote on this theme so frequently and vigorously that he became one of the most uncompromising and conspicuous leaders in the crusade against liquor. He wrote The Temperance Tales (2 vols., 1848), twenty-one stories of a tract-like nature bearing such titles as "My Mother's Gold Ring", "I Am Afraid There Is A God", "Groggy Harbor", and "An Irish Heart", first published in separate issues between 1833 and 1843. These were widely distributed by religious and temperance societies as well as by Sargent himself.
He also achieved prominence as an antiquarian. In 1848 he began a series of weekly articles in the Boston Evening Transcript entitled "Dealings with the Dead" (published in book form in 1856), which in spite of their name did not lack light touches. Under such pseudonyms as Sigma, Amgis, Saveall, and others, he wrote for numerous other publications, and he aroused considerable interest by attacking the coolie trade of the British in India (Evening Transcript, April 16-October 3, 1856) and by assailing Thomas Babington Macaulay for statements derogatory to William Penn (Dealings with the Dead, I, pp. 231-69). Though he showed enthusiasm for the past, his efforts were generally directed towards blasting something offensive to him out of existence. At seventy-five he published The Ballad of the Abolition Blunder-buss (1861), which abuses Ralph Waldo Emerson and others for their antislavery views as violently as his Temperance Tales do the saloonkeeper. Even one of his obituaries refers to him as a man of "harsh prejudices", though it acknowledges the urbanity of his manners in his ordinary dealings and the warmth of his attachment to his family and friends. In 1842 Harvard conferred the degree of A.M. on him, thereby recognizing his public services and condoning his undergraduate rebellion, for the violence of which he often expressed regret. He was preeminently a good hater, but he was a conspicuous man in his day and helped to develop a sentiment in favor of prohibition, besides making rather valuable contributions to local history.