"Slaves, obey your earthly masters" (Ephesians 6:5 and Colossians 3:22) (the easiest one to grep for, since I remember the exact phrasing). Doesn't sound very superseded to me, and Christians continued supporting that right up until the South lost the Civil War (and a fair bit past that in other places) and slavery became politically impractical to defend. So it wasn't a case of a misquotation (by two different sources? really?) being corrected; it was a case of explicitly heretical values being forced on the church at (rather close to literal) gunpoint.

As someone more eloquent than me put it: Christianity had it's chance to rule the world; we call it the Dark Ages for good reason.

Read up on what the Quakers did that whole time.