Why were the jews considered as undesirable? how were they treated in society?

They were "of low physical and mental standards." They were "filthy." They were "often dangerous in their habits." They were "un-American."

"The view was they could not fit into the American orientation toward progress and doing better, and would be forever manual laborers stuck at the very bottom," Diner said of attitudes toward Southern Italians. She said Jews, by contrast, were viewed as "a little too successful, a little too pushy, getting on that American track too fast. They were viewed as competitors."

Religion played a major role in the 19th century, so basically because of their religion some Christian's saw them as abberations. Some were forced to convert and even not allowed in certain professions. Germans had this idea that Jews belonged to a different inferior bloodline too.