“When we simply asked our daughter, "When did you first start feeling like a boy?", she became visibly enraged and lashed back, "I can't answer that!".”
So, he tells you ‘I AM A BOY.’ And you refuse to accept him. Treat it like a trend, or a temporary thing. Yes, he became enraged when you marginalize his feelings in favor of your worldview.
"She proceeded to yell at us for not using her fake pronouns or name.”
I’m guessing he expected this. Probably quite worried about it, but tried to deal with you as, i dunno, parents? Maybe someone who cares FOR him more than ABOUT him?
"She seemed on the verge of tears, but couldn't cry because the testosterone had already started messing her up.”
Oh, man, i went through the same thing with my parents! First person i brought home and declared i was going to marry, was all wrong in their eyes. They told me i wasn’t ready for marriage. They told me i had to consider how an interracial marriage would affect them. They told me what i was feeling wasn’t ‘really’ love. And they told me i was rebelling against them, probably due to my peers. They wanted me to go away for a bit, hang out with some white girls like i grew up with, get back to normal.
Oh.
Wait.
No, no, my parents accepted me at face value and accepted her as a family member immediately. Which is not THE reason my marriage has lasted twice as long as theirs did, but it didn’t hurt.
Also, they’ve been on wonderful speaking terms with me, my wife, my kids, and my grandkid ever since. I doubt that’s in your future.
"For nearly four years now, despite other efforts for a civil conversation, our questions have remained unanswered”
AHAHAHAHA! You think you can tell him that he’s fucking wrong, his identity doesn’t even exist, and it counts as a civil conversation. Rejecting his entire existence and thinking you’re in the right, no wonder he won’t talk to you.
"and she has estranged herself, at nearly 22.”
That’s it, blame him. You have done NOTHING wrong except everything.
“There is no reasoning with these mental patients, which is essentially what they are,”
Yep. He’s the crazy one. Nothing wrong with YOU imposing YOUR reality on HIS head.
"but we also need to be careful to not anger them so they don't do some very stupid & dangerous, like shoot up a school, which has happened.”
Then you might consider NOT DEADNAMING HIM you fucking TWAT WAFFLES!
Not asking the unanswered questions that assume so much.
"I really fear for what my daughter, who's turned to the dark side, hopped up on T, might do someday.”
No, you don’t. People living with ’crazies’ and in fear of the ‘crazies’ walk on eggshells around them. If he thinks he’s Napoleon, you call him Napoleon. You don’t point out AT EVERY CHANCE that he’s crazy. You don’t refuse to accept his claims. You don’t drive him to the point of incoherent rage.
It’s like having a roommate that’s taken hostages. You don’t say ‘no.’ you don’t ignore threats. You work WITH their therapists, not antagonize them.
You’re just making sure everyone knows you’re the victims, here, even when he shoots up a school.