The 1 star reviewers are just proving why this episode had to be made. It's a shame they weren't actually paying attention to it.
Imagine thinking that the world is flat. That's how you look when you so aggressively assert that gender identity is binary. It's not. Clearly it's not. Non-binary people exist. It's natural. And maybe you just won't get it unless you experience it. Maybe it won't click for you. And that's fine so long as you don't start talking about things you'll never understand. I don't understand what it would be like to have a gender. I don't relate to any gender. But I'm not going around insisting that nobody has gender in IMDB reviews.
Perhaps you're just confused. Gender identity, sex, gender expression, and sexuality are all different things. Being closed minded means you'll never understand anything. Which is a shame, because this episode is part of the solution. I appreciate how it's spreading awareness. But you have to be willing to learn with an open mind. Otherwise why are you even watching this wonderful show?