Objective morality refers to the idea that moral principles and values exist independently of human opinion and are based on objective facts. In contrast, moral relativism holds that there are no objective moral truths, and that morality is based on personal or cultural beliefs.
One argument for objective morality is that certain actions, such as slavery, are always wrong and should be universally condemned, regardless of cultural or personal beliefs. This is known as the "moral abhorrence" argument, which posits that certain actions are morally repugnant and should be avoided because they violate basic human rights and dignity.
Covert slavery, or the practice of hiding the fact that someone is a slave, is a form of slavery that is often used to evade laws against slavery and to exploit vulnerable individuals. The fact that it is conducted covertly does not change the fundamental immorality of the act of slavery.
Slavery is considered as one of the ultimate form of human rights violation, and it is considered as morally repugnant by many. Even in the context of war, using human being as slaves is still not justifiable, and as such slavery is considered to be prohibited under international law.
Objective morality, in this case, would assert that slavery is wrong and a violation of human rights, and that it should be universally condemned and actively opposed. The fact that some societies or individuals may believe that slavery is acceptable does not make it morally right.
In contrast, moral relativism would hold that there is no objective morality, and that whether or not slavery is morally acceptable is a matter of personal or cultural belief. This perspective would not provide a strong basis for opposing slavery and other human rights abuses, as it would suggest that there is no objective standard by which to judge the morality of such actions.
Where there is a will there is a way.