Why did people find slavery unamerican was it because of the declaration of freedom

Throughout the 17th and 18th centuries people were kidnapped from the continent of Africa, forced into slavery in the American colonies and exploited to work as indentured servants and labor in the production of crops such as tobacco and cotton. By the mid-19th century, America's westward expansion and the abolition movement provoked a great debate over slavery that would tear the nation apart in the bloody Civil War. Though the Union victory freed the nation's four million slaves, the legacy of slavery continued to influence American history, from the Reconstruction era to the civil rights movement that emerged a century after emancipation.