I feel it's different when you're reading a book or watching a television show, you're seeing someone else's story unfolding. And in something like The Handmaid's Tale or Twelve Years a Slave, sexist and racist societies are depicted, but you connect emotionally to the protagonist and her or his struggle against those systems (and hopefully victory too!)
But when you're playing a game, you're creating your own story. I feel a more accurate analogy for your fiction idea would be telling an author "You can't write a story about a medieval woman ruler/warrior, because that's not realistic."
More like, " You have to come up with an plausible explanation as to why your character is a medieval woman/warrior, because it was unusual in that setting."
There are personal limits on what I will roleplay as but that's more to do with personal discomfort with some roles. After all an assassin or a vampire is hardly an admirable character and I've roleplayed both of those.