You probably look back at the institution of American slavery as I do: with disgust, indignation, and downright horror. Even apart from the unspeakable pain, suffering, and death that white people inflicted on black people, slavery was morally wrong because it treated black people as the property of whites. It was morally wrong because it did not recognize and respect the self-ownership of black people, or the rights that black people have over their own bodies and persons. This lack of recognition and respect is a big reason why we not only react to slavery in the way that we do, but also why we think that our reactions are appropriate. We think that people should react to slavery with things like disgust, indignation, and horror precisely because this white institution failed to recognize and respect the self-ownership of other human beings.
This failure to recognize and respect other humans is already shocking enough. But what if someone were to come along and fail to recognize and respect the self-ownership of all humans, even his or her own? In his first letter to the Corinthians, Paul does exactly this when he says that we humans are not our own, and instead that we belong to God (1 Corinthians 6:19-20). By saying that we humans do not belong to ourselves, Paul explicitly denies human self-ownership. He denies that humans have rights over their own bodies and persons. Then he goes further by saying that God owns us humans, which means that God has rights over our bodies and persons.
Whether intentional or not, Paul is offering a rather disturbing vision of moral reality. By denying our self-ownership and construing God as our owner, Paul is asserting human slavery to God as a fundamental moral truth. He is claiming that each human's moral relationship to God is analogous to that between property and owner, which implies that we, as pieces of property, have no independent moral worth or standing. We are not owed any moral respect or concern in our own right, or because of our nature as persons. God may treat us as he wishes, or have us treat each other as he wishes, and no matter what this treatment consists in, we, as his property, cannot assert any rights or legitimately complain in the name of morality.
To make matters worse, this vision is quite dangerous. As pieces of God's property, what is it appropriate for us to do? You guessed it: to obey God unquestionably. But then all it takes for bad things to result is the willingness and resolve to act appropriately along with the conviction that God wants us to visit discrimination, persecution, or worse on our fellow humans. It is also worth noting that such mistreatment is easier to inflict on other humans if they are thought of as property.
Paul's influence on the world has been enormous, so it's important to be aware of his moral vision and the danger that it poses. Yet it's also important to see that Paul's vision here is just an instance of a general pattern of religious thinking that strips us humans of an independent moral standing and instead allows God to distribute our moral standings according to his wishes and commands. This kind of thinking is all too prevalent, and one doesn't have to look far to see its negative consequences.
We all should reject this kind of thinking because human beings have moral standing in their own right. Human beings are owed moral respect and concern independently of God. We have rights and interests that every other agent--including God--must recognize and respect, where things like race, sex, sexuality, and religion do not diminish or augment the respect that we merit.