I understand, your culture has conditioned you to automatically think of racism and abuse when you hear the word "slavery."
Back in the old days, "slavery" was technically the ownership of another person, although they usually functioned more like servants. They were not beaten, they were not abused, they were not slaves because of their skin color, and they were not obtained by abducting them from foreign lands (well, usually. I think when a civilization conquered another group of people, they made the inhabitants slaves, but that's a different story). Why, in the case of the Aztecs, a slave could legally run away by making it to the temple before his master caught him, if I remember correctly, and with the Hebrews, slaves had the option to go free after 7 years (or at least they were SUPPOSED to, I think the Israelites disobeyed this command at at least one point).
But yes, we are getting off topic D=.