To the Greeks and Romans, being enslaved was not evidence of inferiority. Even though you had the right to own them and exploit them economically, you also knew it could just have easily have been you. These were non-racially prejudiced societies. And you recognized that your slave might not only cut stone in your quarries or weave cloth for you, but he might also teach your child mathematics or design your trireme for you and supervise the freeborn yard workers who constructed it. But a slave was your property, you had rights over them because the gods chose to make them subservient to you and to whoever you sold them to. They were not killed in battle, they were spared, so they and their descendants were condemned to be property. Slave owners could range from from cruel to kind, as do all people. It was all in the hands of the gods. To the ancients, it was not cruel, providing them with life was merciful.

Although not as extreme, we show the same attitude towards our employees, we are placed over them and we have responsibilities which they have contracted to help us fulfill. We do not force them to stay, we reject that aspect of slavery as barbaric, but our relationship with them only survives at our pleasure, and when they cannot fulfill that obligation you are entitled as an employer to dismiss them, even if it is not their fault and even if it condemns them to great hardship. Nothing personal, it's strictly business. To us it is not cruel, providing them with a job was merciful.