The thing to remember about grammar police is that all cops are bad, cops lie, and cops are trained to lie. "Policing grammar" is not as bad as actual cops that can kill and imprison, OF COURSE, but it is an interestingly similar power dynamic at play, vastly different in degree.
The grammar cop pretends (and/or believes themselves) to be helpful, but is in fact exercising power by enforcing arbitrary rules incorrectly, by fiat, and usually against the best interests of society and social conventions.
Like actual cops.
Like actual cops.
The sole authority of a language is the community of fluent communicators in that language. Rules like "they" is plural, or ending on a preposition, or farther/further, or less/fewer, literally/figuratively, the list goes on, are all weaponized bullshit used to exert dominance.
For literally every one of these "rules", you can point to counter examples in print by prominent users of the language, often going back centuries. If it was a real rule, it wouldn't need to be "enforced", because the language users would use it that way.
One exception is someone less proficient in a language who asks for and consents to correction from a fluent language user so that they can improve in their fluency and adherence to common conventions.
I am an awkward signer, and appreciate when my partner corrects my ASL, if it's done in a way that doesn't impede our conversation. She asks the same of me wet English. But that's not policing, it's coaching. It's actually helpful, it's requested, and there's consent.
Language is FOR communication. If you understand something well enough to know what is intended, then it worked just fine. Ie, if you know enough to "correct" it, then it doesn't need correcting.
If you don't know enough to understand what is being said, then your confusion and request for clarification is the correction needed, and you and the other person will find commonality or stop communicating. Either way, no policing needed.