I've pretty much given up on trying to fight the evolution in the meaning of words. Singular "they" was one I resisted for a long time, but it's a lost cause. It still trips me up to hear it or especially to read it: what? did another person suddenly enter this context? I still avoid it myself, and think its use reduces clarity, but it is what it is.
Word usage changes, evolves. A word or a different meaning of a word often starts as slang, then expands to become common usage. It's usually (but not always) apparent from context what the writer means. And, following the guidance of Strunk and White, don't use a fancy, uncommon, or potentially confusing word when plain words will do the job. Writing "he was at a loss" or "she didn't know what to do" is a few more words but much clearer to more readers than "he was nonplussed."
Seriously, I think a lot of what drives these conversations is that people get a bit emotional about what are really somewhat randomly-formed preferences.
However you first encountered the usage of a word will likely heavily influence what you think of as the 'correct' definition, unless you work to overcome your bias by actually studying the etymology and comparing it statistically against current trends. Obviously very few peeps will be down with that noise.
Singular "they" was one I resisted for a long time, but it's a lost cause.
I've had almost the opposite experience from you. I'd long embraced it as the correct word to use when referring to a person of unknown gender or to a hypothetical individual, but having to use it regarding real people caused me problems. When my wife became coworkers with a non-binary person and its usage came up every few days, the better I got at gendering them properly the worse I got at everyone else. First I started accidentally calling her other friends "they", and then I started sometimes referring to any woman as "they". Fortunately that coworker took a job elsewhere before I started referring to men as they too.
I have no objection to avoiding assumptions about a person's gender. It's unfortunate in my opinion that we chose "they" which is gender-neutral but also plural. That is entirely where the issue is for me. I'd have no objection to a singular gender-neutral word (which unfortunately doesn't exist in English). "One" sometimes works, but often sounds too formal. Or reworking the sentence so that "they" is approprate, e.g. "Each person should do it for themselves" isn't terrible, and not too confusing, but better is either "People should do it for themselves" or "One should do it for oneself." The worst is something like "The manager decided that they should do it for themselves" which I see a lot, especially recently. Who is "they" referring to here? The manager? Some other group? It's confusing.
Yes I know that singular "they" has existed for a long time but nobody apparently told my English teachers who would circle it in red every time I accidentally used it.
You didn't invent singular "they" as a child, you were using it because that's what you'd naturally heard and picked up.
Then ignorant teachers told you that you were wrong and they were so successful in brainwashing you, that even after you have learned you were actually correct, you are still trying to argue you were wrong!
> I'd have no objection to a singular gender-neutral word (which unfortunately doesn't exist in English).
Yes it does. "He" is the gender neutral expression in English and has been since forever. It's just that politically correct people get bent out of shape about it.
It isn't gender neutral, it's a gender default. Unless you think it would be correct for the student handbook at an all-girls school to read "every student shall store his books in his assigned locker".
> Yes I know that singular "they" has existed for a long time but nobody apparently told my English teachers who would circle it in red every time I accidentally used it.
I remember reading in the 80s or 90s there was a movement to actively eliminate it.
Yes, I learned (mostly from female teachers) that "he" should be interpreted as gender-neutral if the gender of a singular subject was unknown, e.g. "A writer should always consider his audience" did not imply that only males are writers. It would be nice if people could charitably assume that, but I understand that it can be problematic.
I purposefully and unapologetically try to refer to everyone as "they" these days. A person's gender is rarely relevant (and can often lead to stereotyping), so I see no need to mention it every time I refer to them. And it makes life a lot simpler.
While not strictly improper, this feels needlessly confrontational and pushing of an ideology. You might find you ruffle more feathers than you think by doing this.
Some people seem not to like it (most don't care), but nothing else gets special treatment in language (one doesn't refer to people of different races using different pronouns for example - there are special titles like sir/lord/reverend, but I try to avoid those too), and I think it's good to challenge people's assumptions around this kind of thing.
Word usage changes, evolves. A word or a different meaning of a word often starts as slang, then expands to become common usage. It's usually (but not always) apparent from context what the writer means. And, following the guidance of Strunk and White, don't use a fancy, uncommon, or potentially confusing word when plain words will do the job. Writing "he was at a loss" or "she didn't know what to do" is a few more words but much clearer to more readers than "he was nonplussed."