A Dutch couple visited my workplace (tourist visitor center) and insisted that the French translation on our map was wrong. The reasoning was that "Groenland" shouldn't be there because it was the Dutch word for "Greenland", not the French one. I told them that "Groenland" was also the French translation, to which they chided back, "And how would you know?"
"I'm bilingual. I speak french." I informed
"Clearly, not very well!" they insisted, then proceeded to ask for the wifi so they could use google translate.
Well, I gave them the wifi, and to google translate they went. Sure enough! "Groenland".
They didn't even apologize, they just said "I guess the map is correct then" and left. Assholes.
Didn’t necessarily make anyone look dumb, but certainly made some people feel bad. I lived in Germany for a year after high school as part of an exchange program, and there were several times where I had to make phone calls. I had to call doctors, employers, program coordinators, etc. so I got fairly used to the whole telephone garb in german. I could speak pretty fluently on the phone, but since it’s not my native language I would of course make small grammatical errors and stuff like that. This led to the unfortunate situation where people would assume I was german when on the phone because I spoke well enough, but since I kept making mistakes I was also stupid. People were quite rude to me over the phone, assuming that was due to the assumed stupidity. After revealing I was actually a foreigner they always sounded so surprised and complimentary of my German and were much more helpful and polite afterwards.