Instead of making an argument as to why our culture is mistaken to consider gender a fluid entity, and consider self-identification to be the highest of ideals; I thought I would point you to a beautiful portrait of one difference between men and women. (there are many)
This piece (linked below) also doubles as a great encouragement for married folks. As men and women, we can, unfortunately, relate to each other in ways that are practically gender-neutral. I know I often have. It's one of the things we lost when we lost the manners, expectations, and roles of a century ago. Were those things wrong-headed and oppressive towards women? At times, yes, they were. But, when we threw the baby out with the bathwater, we made it difficult for men and women to take cultural cues in how to relate to one another. This piece shows us one way we can take some of that back. It addresses the realm of communication and I hope men and women will give it a good read. After all, the beauty of our unity, equality, and "same-ness" is that God made us different, and complimentary.