You are choosing to play with words instead of trying to understand what it meant. It can also be that you are trying to make a point of the broadness and the impossibility of providing an exhaustive definition. If we tried, we would do nothing else, for anything: is freedom actually freedom if I am not allowed to harm others gratuitously?

For the law, the slave and the dictator both have dignity, and lower-rank laws will go into detail into what that entails up to the point the judicial system would need to establish if a certain act violates the dignity of a human or not: e.g., "can we kill a dictator nude in a public place and exhibit their remains at the entrance of the presidential palace?" Does it violate their dignity (even if we consider undeserved?)?

Everything depends on definition how else was slavery possible on the US.