What we need to constantly remind ourselves is that Lewis was not writing allegory in the strictest sense of the word. There is no simple correspondence between things in the Narnian world and our world. Narnia and Archenland are not meant to 'represent' medieval Europe, nor does Calormen 'represent' the medieval Islamic Empire. They are unique creations that only represent themselves. In HHB for example Narnia is contrasted with Calormen in that in Narnia 'no maiden is compelled to marry against her will.' But such practices were common in medieval Europe and continued right up to the Victorian age. Lewis is not trying to whitewash the past as some have claimed because Narnia was never intended to represent anything in our world, Rather it is his vision of what an ideal Christian (or its otherworldly equivalent) society might be like.