The actual act of slavery existed as an accepted institution for longer than this computing term has. If we can make slavery a thing of the past (in the western world), we can also update to a more technically correct description of the behavior.

The term "slave" isn't even a good technical term. It would be better to call it a follower or replica which better approximates it's actual role. Not only is it "politically correct" it's also "technically correct", the best kind of correct.