Not completely theoretical. Children born with disorders of sex development are a real thing, and happen more times than most people think. A parent might see a penis and think boy while ignoring completely the lack of testis. Or not have the abilities or desire to test for extra or missing chromosomes.
For centuries people that exhibit or otherwize claim to be\feel\know they are not what they outwardly appear to be have been celebrated for their abilities to under both sexes and were seen as a gift from god. Some groups termed them third-gender peoples going back before the 7th Century CE. I can see why some people view transgenderism as a defect or mental issue, they lack the knowledge of history and are ignorant of the past. And because of their upbring\religious affiliation, refuse to examine their own ignorance and choose to fall back on what they were taught.
As for gender being a construct there are plenty of guys on this board that believe just that, as do I just in different ways. When calling a guy a bitch or pussy for wanting to stay home and raises their kid while the mother works, or dressed up and paints their nails because their 5 year old daughter needs someone to play with, or drives a Chevy Bolt. Somehow when it's done in a derogatory manner it's acceptable to do so.
As for overriding chromosomes I think we can all agree that we aspire to be the thing we cant be. A 5'2 guy wanting to be a forward for a pro BB team, a scrawny guy wishing to be a pro football player, someone who wishes they could sing like some of the greats or play like them, and if given the option to pop a pill or inject a chem they would in a heartbeat, just like the guys here, myself included, do.
I would challenge anyone to spend a month in the shoes of someone's body that isn't the right fit for them, to go out in public dressed as the opposite sex and take the abuse that those that do take, and then come back and say that people are just choosing that feeling and are doing it for attention.
As I said to one of the other posters here, the Christian God was the first person to use plural pronouns but yet that seas to be OK with them.
I don't claim to know everything, and I'm sure there are people that do it just for fun. But with what I've been through in my life, what someone else choices for themselves and has absolutely zero impact on my daily life, I could gives two fucks about.
I know I didn't answer all you questions and rambled a bit, I have that tendency, but I hope some if it was responsive.
