why was it important for the nativists to make the white race seem to be smarter and more capable than non whites

When the nativist movement started (the know nothing party), it was suppose to make other races and immigrants seen stupid and dehumanize them. This creates fear for Americans and made the population feel that immigrants were ruining America and that they were taking our jobs. If they made white people seem more powerful, most of America could get behind them since we were majority Caucasian and made other races seem lower than us leading to anti immigrant legislation such as the Chinese exclusion act and the laws passed in the 1920s that placed a percentage on how many immigrants from a certain country or area could enter the US.

because then it would dehuminaze non white people, making it easier for laws to be passed limiting their rights and access to certian things. This led to stricter immigration laws, increased racism, people of color having less rights and not being in positions of power, etc