Some reasons slavery should be abolished?

It is cruel, unfair, and degrading to enslave another human being. As Abraham Lincoln once commented in a private letter, if slavery isn't wrong, then nothing is wrong. If you believe that it is within your rights to deprive another human being of any self determination and treat him or her as a domestic animal, belonging to you, then you would be hypocritical to claim any human rights for yourself, either. Either people have rights or they don't. And if people have rights, they must not be enslaved.