Why did abolitionist William Lloyd Garrison burn a copy of the U.S. Constitution?

In the North, the abolitionist movement against slavery that began in the 1830s gained new momentum in response to the Fugitive Slave Act. In 1852, Harriet Beecher Stowe published an antislavery novel, Uncle Tom's Cabin. The book became a sensation, and ranks among the best-selling books of the nineteenth century. Its powerful condemnation of the greed and brutality of slave owners struck a chord with many Northern readers.

The Fugitive Slave Act led some abolitionists to complain that the federal government had sided with pro-slavery Southerners and had forced Northerners to support slavery by capturing and returning escaped slaves. In response to the Fugitive Slave Act, a growing number of Northern abolitionists began to suggest that a opponents of slavery should defy the act and adhere to a law higher than the U.S. Constitution. In 1852, former slave and abolitionist Frederick Douglass delivered a fiery speech, What to the Slave is the Fourth of July? Douglass criticized the hypocrisy of celebrating independence in a nation whose laws kept four million people in slavery. Two years later, abolitionist leader William Lloyd Garrison marked the Fourth of July by declaring that the U.S. Constitution was a pro-slavery document and urging that the Northern states leave the Union. To emphasize his point, Garrison held up a copy of the Constitution and lighted it on fire. Abolitionists, tired of political debate and compromises over slavery, increasingly believed that only a sudden, decisive moral attack against the evils of slavery would bring freedom to slaves