When people argue that because something wasn't true in history, it can't be in fiction either. Even in fantasy.
...And it's not even the big things, they'll accept dragons and daemons and guys with swords that weigh twice their own weight but show them potatoes in LOTR and they'll start creaming about anachronisms, show them women on battlefield and they'll cry about feminists ruining everything ...apparently just seeing horses of the wrong breed will set them off on a rant on how you are bad-wrong if your fantasy world with elves has horse breeds that weren't seen in Europe during medieval period.
Guys, there's a difference between historical fiction and fantasy.