zahavasdad,
When you speak another language besides english people get paranoid and THINK you are talking about them even if its not true.
I agree that in most cases, common courtesy dictates that people should avoid conversing in a different language when around others who don’t speak that language. The paranoia you describe, however, is not as much a result of the lack of courtesy as it is a reflection of the listener’s xenophobia.
For some reason Yiddish Speakers never got this message and do tend to speak Yiddish even though they know everyone around them speaks english
I work in an office where a lot of people speak Chinese, and many times in break rooms and meeting rooms I hear people conversing in Chinese around non-Chinese speaking Americans. I have lived in areas with a lot of Spanish speakers, who converse in Spanish around English speakers. Just the other day two women in a store were conversing in Russian in front of me at the checkout line. Everybody does it, so why are you picking on Yiddish speakers?