Harriet Beecher Stowe
Even if slavery is opposed and hated by the northerners, they don't take active initiative against the abolition of slavery.
In point of fact the system of slavery is itself an evil. Even the pious and educated citizenry of south perform the system of slavery. Even the respectable citizenry has been performing this system. According to Stowe the system of slavery itself is an evil. So long as this system lingers in the society, the souls and the hearts of even the pious become mean and corrupted. Even the pious and educated become so corrupted that they downplay even the basic human sentiments like love and affection.
To illustrate this interpretive claim lets cite one event from the text. Among the slaves whom Haley has brought and is taking to market is a young woman named Lucy with a baby, whom Haley sells to a man on the boat. Haley became so greedy and monstrous that he sold a son of a slave mother when she was sleeping on the boat. Haley became that much lowly is his selfish interest. It is the system of slavery within which Haley became corrupt.
Mr. Shelby was pious. He was merciful in his treatment of his Slaves. He had no brutal intention to separate Uncle Tom from his wife. But the mounting pressure of debt forced him to sell Uncle Tom. Even Evangeline St. Clare promises freedom for Uncle Tom. But he can't take active action at the right time. Even Mr. Bird, who subscribed to the convention in the Fugitive slave Law, simply becomes influenced only after having seen the plight of Eliza and her little Harry. Even those who had a liberal nature are presented as handicapped to eliminate slavery. Harriet Beecher Stowe calls slavery as an evil. She attacks the northern and the southern readers for not taking immediate action towards its abolition. Hence, Uncle Tom's Cabin is a polemic novel.