[OmikronWarrior]

Russia had a very odd form of slavery. People essentially sold themselves into it for a given time frame, usually a year. The practice obviously developed as a way to hire laborers for farms. However, since slaves did not pay taxes, in the 16th century a lot of Russian elites sold themselves into a gentler kind of slavery to get off of tax rolls!

In general, however, I'd say slavery is an evil institution, but its existence does not doom the entire civilization to being evil.