Daniel Abraham on misguided argument from "authenticity" in defence of certain types of fantasy:

The idea that the race, gender, or sexual roles of a given work of secondary world, quasi-medieval fantasy were dictated by history doesn’t work on any level. First, history has an almost unimaginably rich set of examples to pull from. Second, there are a wide variety of secondary world faux-medieval fantasies that don’t reach for historical accuracy and which would be served poorly by the attempt. And third, even in the works where the standard is applied, it’s only applied to specific, cherry-picked facets of the fantasy culture and the real world.

(Some good comments, too, and sometime I'd like to have a more thorough discussion about Saladin Ahmed's point: "I agree with every point here. Yet and still, if your quasi-medieval blacksmith shows up wearing sneakers, I will cry foul. For others bailed hay is a foul. Interesting questions of thresholds folded in here, is all I’m saying.")