It would be really interesting to have this much undeserved confidence. Who in their right mind thinks they have a better understanding of a language than an grandma who's been speaking it for her entire life? And on top of that, he goes in and tries to "correct" them. It sounds like a recipe for an extremely awkward relationship. Here are some more entitled people and their demanding boldness, as well as some facepalm moments of mystifying dumbness.
The English language has some confusing peculiarities to it that result in English struggles, but heck, most languages have some phonetic and semantic weirdness winding through them. And English isn't the only strange language. Here's a post defending the English language and how it's not the only weird language out there.
We love nothing more than a good old fashioned language translation fail. Languages can be wildly confusing, and sometimes that goes on to inspire absolutely hilarious misunderstandings between people that would otherwise be getting along just fine. In this case though, we learn that this particular misunderstanding was the straw that broke the camel's back, and apparently this guy was a dang "side guy."
What happens when you spend an entire year convincing people you have an accent, when in fact you speak perfect English?
Translation fails inspire all kinds of hilarious confusion between two perfectly rational human beings. In this case, we have a customer unknowingly repeatedly pleading for nothing at all. If you're the bartender on the other side of that mishap, do you let the oblivious stupidity persist, or do you correct the translation fail as soon as possible? Could be a tough call if you end up wanting to have some fun with it.