Question: Why was the lead character in Harriet Beecher Stowe's a derogatory epithet?

Context articles: Harriet Beecher Stowe House (Cincinnati, Ohio)
Tom show
Edward Beecher
Domestic realism
Forrest Wilson
Harriet Beecher Stowe House (Brunswick, Maine)
Park Church
Lyman Beecher
Uncle Tom
Oldtown Folks

The Harriet Beecher Stowe House is a historic home in Ohio which was once the residence of influential antislavery author Harriet Beecher Stowe, author of "Uncle Tom's Cabin".
Tom show is a general term for any play or musical based (often only loosely) on the 1852 novel "Uncle Tom's Cabin" by Harriet Beecher Stowe.
 The novel attempts to depict the harsh reality of slavery.
 Due to the weak copyright laws at the time, a number of unauthorized plays based on the novel were staged for decades, many of them mocking the novel's strong characters and social message, and leading to the pejorative term "Uncle Tom".
Edward Beecher (August 27, 1803 – July 28, 1895) was a noted theologian, the son of Lyman Beecher and the brother of Harriet Beecher Stowe and Henry Ward Beecher.
Domestic realism normally refers to the genre of 19th-century novels popular with women readers.
 This body of writing is also known as "sentimental fiction" or "woman's fiction".
 The genre is mainly reflected in the novel though short-stories and non-fiction works such as Harriet Beecher Stowe's "Our Country Neighbors" and "The New Housekeeper's Manual" written by Stowe and her sister-in-law Catharine Beecher are works of domestic realism.
 The style's particular characteristics are:
Robert Forrest Wilson (January 20, 1883 in Warren, Ohio – May 9, 1942 in Weston, Connecticut) was an American author and journalist.
 He won the Pulitzer Prize for Biography or Autobiography in 1942 for his biography of Harriet Beecher Stowe, "Crusader in Crinoline: The Life of Harriet Beecher Stowe" (Philadelphia: Lippincott, 1941).
The Harriet Beecher Stowe House is a historic home and National Historic Landmark at 63 Federal Street in Brunswick, Maine, notable as a short-term home of Harriet Beecher Stowe and Calvin Ellis Stowe.
 Earlier, it had been the home of Henry Wadsworth Longfellow as a student.
 It is today owned by Bowdoin College.
 A space within the house, called Harriet's Writing Room, is open to the public.
Park Church runs the length of an entire city block in Elmira, New York.
 The church was constructed from 1874 through 1876, replacing its much smaller, wooden predecessor.
 It was designed by Horatio Nelson White.
 The design of the limestone and brick church is highly ecelectic.
 Besides its architecture, the church is significant for its congregation of abolitionists and humanitarians.
 From 1854 until his death in 1900, Thomas Kennicott Beecher was the pastor of Park Church.
 Beecher, together with his twelve siblings including author Harriet Beecher Stowe, was brought up by liberal reformist clergyman Lyman Beecher.
Lyman Beecher (October 12, 1775 – January 10, 1863) was a Presbyterian minister, American Temperance Society co-founder and leader, and the father of 13 children, many of whom became noted figures, including Harriet Beecher Stowe, Henry Ward Beecher, Charles Beecher, Edward Beecher, Isabella Beecher Hooker, Catharine Beecher and Thomas K. Beecher.
Uncle Tom is the title character of Harriet Beecher Stowe's 1852 novel, "Uncle Tom's Cabin".
 The term "Uncle Tom" is also used as a derogatory epithet for an excessively subservient person, particularly when that person is aware of their own lower-class status based on race.
 The use of the epithet is the result of later works derived from the original novel.
Oldtown Folks is an 1869 novel written by Harriet Beecher Stowe.
 Oldtown is a fictional name for the real town of Natick, Massachusetts, the native home of Harriett Beecher Stowe's husband, and many of the ideas in the book come primarily from his memories.
 "Oldtown Folks" has claim to be read as a religious novel and often discusses Puritan lifestyles as well as Calvinism and Arminian theology.
 In addition to these concepts and also the nature of a utopian society, this novel focuses on the question of reproduction and mothering.
 Written from the perspective of the main character, Horace Holyoke, the novel follows his life in post-American Revolution New England.
 It is divided into two volumes by the age of Horace and his friends.