The ideals of life, liberty and the pursuit of happiness are essential to the way of life of America. These ideals are present in the Declaration of Independence, and were meant to guide legislation in the nation.
However, slavery is a clear violation of all these values. Slavery is incompatible with life, as slaveowners could take the life of slaves with impunity, since they were considered to be property. Moreover, slaves were considered slaves the moment they were born, which meant that they never had the opportunity to have a different life. Liberty is clearly incompatible with slavery, as slavery by definition refers to a person who is not free. Finally, a slave could not pursue his own happiness, as his life was completely tied to the desires and interests of his owner.