STEREOTYPES
Even before 9-11, Americans had multiple prejudices and stereotypes towards Arabs. They are usually spread by the mass media. They are represented in different media, such as cinema, literature and theatre. All those stereotypes are normally negative.
"Arab men being portrayed as terrorist or as wealthy oilmen and Arab women being portrayed as sex object".
Those stereotypes are very negative for the arabs and the muslims living in the USA, because they are always treated differently, even if they consider themselves as Americans. Some psychologist also showed that those prejudices are not only causing psychological problems, but also physical ones. When an American was feeling armed by an arab or a muslim, he would be more likely to use physical violence, and not only physiological ones.
After 9-11, those stereotypes went up and a big part of the population was scared of arabs and muslims. After that event, Americans, but also people around the world, where generalizing all the arab. They referred to them as terrorists and bombers, because the world trade center was attacked by muslims. Now, not only the population is stereotyping the arabs, but the police also. It has become very difficult for arabs to cross the borders in airports. Police always target them first.
http://www.sciencedirect.com/science/article/pii/S0022103108000681