Final answer:
The argument for restricting Asian and South Asian immigration was based on racial prejudice and protecting American jobs and cultural homogeneity. Anti-Asian laws were influenced by economic concerns, and politicians exploited nativist attitudes. Legislation evolved over time, culminating in the more inclusive Immigration and Nationality Act of 1965.
Step-by-step explanation:
The argument used to legitimize restricting Asian and South Asian immigration largely stemmed from racial prejudices and economic fears. It was argued that Asian immigrants threatened American jobs and culture. Laws like the Chinese Exclusion Act of 1882, the Immigration Act of 1924, and the dictation tests under the White Australia Policy were passed to explicitly restrict immigration from Asia based on racially discriminatory ideologies. Nations aimed to protect the idea of American and Australian homogeneity, often under the pretext of preserving economic stability and social order.
In the United States, the argument was further solidified by nativist attitudes. Politicians and labor groups fueled anti-Asian sentiment by blaming Asian immigrants for economic and social issues. The quotas set by the McCarran-Walter Act, continuation of ideologies from earlier laws such as the Emergency Quota Act, and the National Origins Act emphasized restricting immigrants that were deemed non-assimilable and who were believed to pose threats to the 'racial purity' of the nation.
Ironically, despite these exclusions and restrictions, specific provisions allowed for the migration of family members of current citizens and individuals with valuable skills. Such policies started shifting with the Immigration and Nationality Act of 1965, which eased the restrictions and resulted in the formation of new Asian and Latin American immigrant communities.