No, They should not. No human being should be classified as lower than anyone else, We're all humans, Inside and out and we all deserve the same rights, No matter sexuality, Skin color, Religion or gender, We're all equal. Everyone deserves to be paid for their work and not forced to work for nothing in return.
Right now the only only nations where slaves exist are in the oil rich arab nations and Malaysia North Korea and certain Asian countries and certain African countries partnered with shady Europe.
Then there is prostitution which could be considered slavery.
You can't own someone because it is wrong. They are not animals they are human beings. Sure lots of people do it and get away with it but God will punish every wicked person and will punish all the crimes they committed and every evil word that came from their mouth.