Love /
Dating in Poland not able to speak Polish [24]
nonetheless hardly excuses such provincial rudeness or insensitivity
I know exactly what you mean, because after being in South Africa 2 months, I was told that my English improved :-} by an Afrikaans individual whose English wasn't exactly flawless... And I came to South Africa having learned English for over 20 years, out of which 10 years was spent in UK, living and working among English people... Somehow, I think he thought he was being appreciative, so I decided not to take offense... Annoying as it may be, I really think those people did not mean to be rude to you.
As for some people "thinking" they speak language better than somebody else... Yes, this can be very frustrating, especially if you are getting nowhere in the conversation... But what do you do? Try to prove them wrong (in which case they get defensive and whatever you are trying to get them to do will probably not happen...) or let it done and over with as soon as possible? Sometimes the latter works better than bursting their bubble.