Two things:
(1) I swear I'm singled out at the airport just because they can't decide if I'm hispanic or muslim--once I went to this event with half Egyptians and half Americans, and nobody knew how to talk to me. The Egyptians would try to speak Arabic to me, and the Americans just kinda looked at me until I would start talking to them in English... On the whole, it was a fairly uncomfortable thing...
Meanwhile (perhaps as a result of looking either muslim or latina, perhaps not), I get screened at the airport a lot. I don't really care because I'm not doing anything wrong (though I did think they might catch on when I was trying to not declare a rug I bought in Morocco--where they also spoke to me in Arabic, by the way. I quickly learned how to say, "I don't speak Arabic" in Arabic, which mainly served to surprize them and spur them to talk more, to which I always repeated "I don't speak Arabic..." and shook my head until they got it)
(2) I used to work at a bank, and one day a black man named John Smith (or something equally common and "non-ethnic" or whatever) came in and was upset because the bank had not approved his loan. He said, "I have excellent credit! Is this because I'm black?"
And I said, "Sir, I can promise you that it is not. I can understand how it can feel that way sometimes. It happens to me too--When I go through the airports, I get stopped all the time...So you get to thinking, this really can't be random, because it's always me. They're always stopping me, always swiping my bags for bomb material... In fact, once I was going through customs and an agent said to me, in Spanish, "Where are you coming from?' and I just kind of looked at him and said, "Huh?" And he said, "Oh, I'm sorry, I thought you were latina--come right this way..." and preceeded to search my bags...
"So I understand, I understand how it can feel that way sometimes, but the loan processing department is in Southern California, 500 miles away, and no one over there knows what you look like because they've never met you... So I understand, but I can promise you, this is not that. If you want, I can get the manager for you and she can explain to you what happened..." At which point he relaxed visibly...
The moral of the story: sometimes things are based on outward perception, and sometimes they're not... I think we just have to do our best to give people the benefit of the doubt and do our best to let it just roll off, otherwise we'll just spend way too much of our lives being angry...