It seems more of a joke about gender politics rather than specfically making fun of trans people. It is poking fun at the idea that assuming someone's gender is somehow problematic and a big issue that needs to be solved. As if like transgenderism is actually a common thing rather than for the most part ideologically driven bullshit. Or that misgendering someone is the worst thing you can possibly do. Sure, if someone does it on purpose, they're being a bit of an ass, but if it is done accidentally and then they correct themselves, it is not the end of the world.