You know the rest!
I have often wondered how it is that people are happy to make total asses of themselves by assuming things about other people.
Just this last week, I saw a sad posting on Janglo from a young desperate girl. She wanted advice on how to stop people "assuming" that she wasn't Jewish because of her looks. She said people often asked her why she converted etc... I myself am often asked "where are you from in America." Generally it's Israelis asking me this question so I am not too bothered. But when I reply that I am from Australia their voices soften while they happily explain how they have ALWAYS wanted to go there, followed by the inevitable question "so what are you doing here, why would you leave Australia to come HERE?"
Another assumption is that I speak Russian. I cannot tell you the number of times a checkout person, or an old woman on the street will start conversing with me in Russian, a relieved look on their face that they have finally found someone to speak to who can understand them, only to be offended when I sheepishly explain I cannot understand what they are saying. In fact the cleaning woman in our building does it to my husband. I don't think he looks anymore "Russian" than the average English gentleman, but she insists on speaking to him in Russian everytime she sees him and insists to me that she knows he really can understand her!
This reminds me of the time we were visiting my husband's family in England for Sukkot. There is a cute, small kosher sandwich place in downtown London and we had made arrangements to meet a good friend of ours for lunch. Outside this lunch place Habad had set up a tent-like pop-up sukkah. There were 4 or 5 young Habad boys walking around going "are you Jewish, excuse me are you Jewish?"
My friend, on being approached with this question, politely informed them that it is rude to go up to a person on the street and say "are you Jewish?" She suggested that instead they should ask, "excuse me, do you want to bench Lulav? And if they answer no or what is it then you know they aren't Jewish and you thank them and move on."
Just then a black (? is this PC still?) woman walked past and the same young man went up to her and said, "excuse me would you like to bench Lulav?" To which she replied, "yes please, what is it?"
:)