Dictator needed

Even if there were some rule about "they" being plural-only (that seems to have been discussed well already), consider that what you're saying is: you are more worried about following some arbitrary rules to show off how well educated you are, than you are about how this frustrates and excludes actual real people who already have to deal with way too much of this BS.

And no, saying "well they should just decide that it doesn't exclude them" doesn't actually help. It's not their job to compensate for your thoughtlessness just so you can win some imaginary argument with the English language.