The story is make-believe and doesn't affect our personal sensibilities, outlook, or social norms, unless you're really that weak willed that you let it affect you. Obviously it hasn't, or there wouldn't be complaints from people whose beliefs find such a thing offensive. It's a fictional story, and slavery is one of the elements of a different world with a different culture, both of which don't actually exist. If you're incapable or unwilling, of compartmentalizing and distinguishing between reality and a fantasy which has no actual bearing, effect, or influence on the real world whatsoever, if you actually hate it that much, well, no one is forcing you stay and continue reading, are they?