Spiritual diginity is the idea that a human being has worth, by virtue of being born. The soul is valuable. But certain actions can devalue that spirit. We're not necessarily talking about
sin here. This is more along the lines of reducing the human entity to the level of an animal. Slavery destroys the spiritual dignity of a person. It takes from them their rights to live as a human and have control over their life. Any action that co-opts the ability of one to choose in their life is generally ruled unethical by modern philosophy. This is the underlying basis for the
United Nations'
Declaration of Human Rights.
"If you get a man a fish, he eats for a day. If you teach him to fish, he eats for life." To extend this trite phrase, if you get him a fish every day, eventually he is dependent upon you and his ability to function as an individual and to choose the path in his life is hampered because your will now plays a part in his decisions. By teaching him to fish, you increase his spiritual dignity. By fishing for him, you decrease it.
It is generally not considered unethical for a willing decrease in freedom of action between or among people. Marriage. Friendship. These are two examples of people willing choosing to be less of an individual and more of an integrated unit. These are not decreases in spiritual dignity, as they are undertaken willingly and with partners who have something to add to the relationship.