New Year Grammar Grouch 2

This should be pretty simple.
there = a location, any place which can’t be called “here”
their = the possessive of they — “It’s their choice.”
they’re = a contraction for “they are”
All pronounced very much alike, though actually the last one offers a subtle difference most people don’t catch in ordinary conversation. That’s a function of our sloppy American mispronunciation of English, which is a known contributing cause of much misspelling. While the American dialect isn’t supposed to sound like any of the various colloquial dialects from the British Empire, it does have it’s own precision if we bothered.
Did you ever notice most popular singers perform English language songs with a flattened American accent? And why does one seldom see reference to a Canadian accent? Newfies, of course, but the great North American Heartland is pretty vanilla all the way up to the ice. Each regional dialect is the result of particular waves of immigration. I guarantee George Washington bore a proper upper class British sound.
I reject all arguments any one dialect is pure or original English. Few of us could understand spoken Middle English, much less Old English. Nor is “proper” necessarily whatever folks do where you are located. Proper is whatever those most careful in your area taught you, but includes your relative ability to absorb and blend in with what you hear around you when you move to another place.
It isn’t proper to correct anyone’s grammar unless it is your civil duty. That is, if you are a teacher or custodial/leading adult of children, your job is to help them get it right for the context in which they live at the time. If your relative position otherwise qualifies you as someone expected to do this for whatever reason, in some contexts you can get away with it.
Otherwise, civility requires you avoid correcting others. Granted, you can subtly do a lot of correcting simply by making sure you do it right yourself. Someone does it wrong, and you simply stick to your guns and ignore their mistakes, with the possible exception of asking what they meant. Be tactful.
I get grouchy with folks running around correcting everyone else. I do all my grammar grouching where people can safely ignore me.