Just keep in mind that all those Star Wars wikia links are mainly "legends" stuff and not actually canon.
Sidious is a Sith and certainly not opposed to slavery. We also see in TCW that the Zaigarians (spelling?) are looking forward to a renewal of the slave trading ways of old. Slavery certainly exists in the Empire and around it, but not necessarily overtly. Remember, there is still a Senate right up until Ep. IV, even if Sidious has largely made it a rubber stamp for his decisions, and Tarkin and Vader still have to tread at least a little carefully when they abduct Princess Leia ("only you could be so bold"), ensuring that they have the evidence they need to get away with it. The Empire is not yet a Sith empire, it is still very much transitional. IMO, you can resolve the discrepancies in cannon quite adequately by saying the Empire has slavery in practice, not in name.
Edited by knasserII
