From casual conversation with some Chinese associates, I get the impression that they see Arabs, Iranians, Jews, Turks - West and Central Asians in general - as noisy, emotional and confrontational people, all traits that the Chinese don't admire too much. Physically, they were considered unattractive. Their hairiness (relative to Chinese) was also cited as an unappealing feature.
Sometimes I wonder how far back these attitudes go. According to the book "Familiar Strangers: A History of Muslims in Northwest China", a Yuan dynasty writer made allegations about the body odor of Chinese Muslims of West Asian/Central Asian descent: "Even when they bathe, the Huihui (Muslims in China, typically of West Asian/Central Asian descent) still stink."
A Ming dynasty document [Da Ming lv jijie fuli] states:
Huihui are shaggy with big noses... Their appearance is vile and peculiar...
A 17th century official recommendation on controlling Muslim unrest in Northwest China reads:
Forbid them to breed horses or to keep weapons... let them all cultivate the soil, and so gradually allay their ferocious natures.
It seems that modern stereotypes carry an echo of medieval prejudices.