To each his / her own. Some people may get offended, some not.. It depends on the person / situation really. The common annoyance is people tend to typecast based on nationality, which is a total NO.

Like, while I am proud to be an INDIAN, I feel offended if people assume that I am from Kerala and it is a crime not knowing Malayalam being an INDIAN.

But then again, why waste time frowning at a person you may not even meet again in your lifetime.