Random observations:
It's (at least) the directly Latin based and more distantly Latin based "Germanic" languages that make difference between male and female personal pronouns.
There are many languages that don't and those languages work just fine.
There's a thing called "gender dysphoria". Look it up. So, when people "almost correctly" say that sex is the chromosomes and gender is a choice that can give a wrong impression. It's not necessarily a choice. You don't choose that "From now on I'll start feeling like a man although I was born as a biological woman". (Just as you don't choose to be hetero/homo/bisexual.)
You can choose what to do about it and doing something about it involves psychiatric counceling, but not because you are crazy, but to make sure that for example hormone treatment and/or corrective surgery is really the right way to proceed. It may not always be.
A man is a man and a woman is a woman, but what qualifies as "man" or "woman"? It's ultimately up to the person themselves. Transitioning sometimes leads to very convincing results and at other times there's some "uncanny valley". But if we then feel "icky" it's our problem. And there are masculine women and feminine men -- just born that way -- even without transitioning with hormones and surgery. And our prerogative then is not to date and mate them if we don't wanna. And some people are just plain ugly for whatever reason, but ugly people are people too. 😉
There's a difference between "modern invention" and "modern discovery".
There's talk about "social constructs". Some of those may be "modern inventions" i.e. people making things up. I don't have any more specific opinions about that topic. I haven't bothered too much about the "woke" culture, Social Justice Warriors, safe spaces and trigger warnings, but enough to know that sometimes people are just silly and there apparently are some real problems e.g. in some universities.
Then there are "modern discoveries" where we learn about things that have already existed and hopefully change our behaviour accordingly. A lot of the sexual identity stuff probably belongs to this category, so it's fact, it's science and calling it a "modern invention" is just inability to accept new information that is against old personal beliefs, ideas and opinions. (Absorbed from the culture and social circles in which we grew up, so it's not really just an individual's own fault.)
Intentional misgendering is a thing. You might not have realized that somebody is trans, but once you do, you start calling a female "him" or a male "she" just to fight against something that you personally don't like. It happens.
Who defines the "greater good"? E.g. Sam Harris has written and talked about the topic of science vs. moral questions, but "well-being" can be a hard thing to define, quantify and measure. And cultural relativism can get in the way too: "Who are we to judge?" etc.
You could say that freedom of speech grants people the right to call you a "dickhead" but the other side is:
- Freedom of speech isn't freedom from consequences, so there can be some.
- It's not great for your personal well-being, so which one weighs more? Somebody else's freedom of speech or your personal well-being?
Just call a him a "him" and a she a "she".
But I don't know what to do with the "It's complicated" people. Treat them with respect, maybe(?)