Line Manager just "come out" as Non-binary

[SpinningTooFastWantToGetOff]

My line-manager emailed everyone in the office last week to say she was non-binary and we should use they/them pro-nouns.
Today I inadvertently called her she in an email to a colleague in another office, but line-manager was copied in, plus her line-manager. Are you keeping up?
My line-manager responded to the email and added at the bottom a reminder about her pro-nouns.
I do not believe in the gender identity ideology and so object to being told to speak in an unnatural and incorrect way, but what I am incandescent about is being called out in front of 2 other colleagues.
Am I over reacting?

First of all, OP, I understand you. It'd drive me bonkers. Still, here's my sober take on the situation as per my best professional judgment:

In a nutshell, OP, your problem is that you already don't get on well with your line manager / have had work-related issues. As a member of senior management at my own workplace, if this ended up on my desk somehow, I'd have a hard time overlooking it. And, I suspect, so may any HR department. Remember that the primary function of HR, whatever they tell you in their employee marketing newsletters, is to make sure your employer doesn't get their arse sued off or reputationally damaged by its own personnel if push comes to shove.

If you're looking at your description of the situation under the worst case (from OPs angle, not the manager's) interpretation you could end up with a narrative that boils down to "employee who was passed over for a promotion/lacked the courage or ambition to gun for it has a hard time adjusting to new management and has ended up being a bully when other, only more senior employee had issues with their health and eventually came out as non-binary".

I'm not saying it's like this at all. I am, however, saying it may be possible, perhaps quite easily so, to spin the situation in this way.

That's why I would advise you to speak to HR/your union about the performance concerns and leave the pronouns stuff out altogether.

I realise this is frustrating. But then, the best piece of advice I've ever had in a situation where I was going up against a higher up has come from my shark of a solicitor, who dissected my the situation and my personal position in the firm with clinical coldness and advised me to go ahead because I was going to win the sympathy vote as well as the race for corporate PR points if push came to shove. Hired him on the spot. He's probably a psychopath - but he has a very good point there.

Sadly, I don't think that's really a given in this situation.

I really, really appreciate all your thoughts and advice.
My current plan is to say nothing about pronouns, just communicate as little as possible so I don't need to be reminded again.
Yeahlike I understand exactly where you are coming from, although senior management are aware of the situation and my unhappiness with my lack of management.
My problem and it is my problem, is that I have to work with someone for whom I have no respect. This has nothing to do with the NB thing, I lost respect several months ago.
So I will just shut up and get on with my work. I am trying to chill and just filter her out.

But I won't be using her preferred pronouns.

Best wishes and good luck...let us know how it progresses.........I'm glad to not be in any similar situation myself - as I'm no longer in a highly visible and/or public workplace. I used to teach - and even just 10 years ago this was just not a 'thing' in schools, or with pupils....and if it had have been I just know I would not be able to do as told - against my own judgment or instinct.

^Hans Christian Anderson's fable The Emperor’s New Clothes, 1837
Anderson's tale involves a vain king who was preoccupied with his appearance and his wardrobe. A pair of swindlers took advantage of this by pretending to be able to weave the finest cloth, which couldn't be seen by people who were either unfit for office or were particularly stupid. The king decided to have a suit of clothes made from the fabric in order to test which of his courtiers was unfit for office. As he didn't want to appear stupid or unfit for rule himself, he pretended to be able to see the new clothes, as did all of his courtiers. He paraded the 'new clothes' through the streets and the onlookers, also not wishing to appear stupid, all admired them. A small child, who didn't understand the apparent necessity for pretence, piped up 'But he has nothing on!'. The bubble of pretence burst and soon all the onlookers were repeating what the child had said, whilst the king continued the procession, attempting to maintain his dignity by pretending that nothing had happened^

So, the meaning of the expression is clear from the story. It is used in contexts where people are widely acclaimed and admired but where others question whether what they have created is of any value. Modern-day examples might be the highly priced work of conceptual artists or the more avant-guard products of fashion designers
The phrase bears some similarity to another modern-day expression - the elephant in the room. An essential factor with both phrases is the willingness of people to engage into an unspoken contract to wilfully disbelieve what they know to be true

Let us know how it goes!

If you take this to its logical conclusion, to refer to members of Islamic State you should use "IS-MitgliederInnen", which nicely avoids oppressing all of the genderqueer suicide bombers out there (whom IS of course embraces with open arms, to save them from the kind of awful persecution meted out to the OP's line manager).*

Samarrange I snorted tea out of my nose when I read that

If you take this to its logical conclusion, to refer to members of Islamic State you should use "IS-MitgliederInnen*

... though, to be fair, "mitglied" is a neutral (no, not having a boring day at all, most definitely did not confirm this using a dictionary). Which would mean "Mitglieder*Innen" would exclude males, surely?

Then again, it also apparently literally translates as "fellow/co member". Whereas "member" means precisely what it means in English, too. From that perspective, it would only ever include people with a penis (naturally grown or surgically created, I suppose) but of all genders?

Yeah ... definitely not a slow day at the office ...

@SpinningTooFastWantToGetOff - pronouns aside, it sounds a really, really miserable situation, and I hope it's resolved positively for you in the relatively near future.