Their ideal is free movement of goods, labor, and capital, leading to the liquidation of the nation-state as an impediment to making money. This is globalism, and make no mistake, it implies world government in the long run. Per capita GNP is the rational goal, and immigration lowers this by diluting our economy by poor, i.e. unproductive, workers. By adding poor people, while increasing the profits of the rich, immigration increases social inequality. Several thorough studies have shown that any economic benefits of immigration are very small, and mainly go to the immigrants themselves.
Immigration undermines the social, cultural, and ethnic cohesion necessary to sustain our society.
These factors are more important than people think. We are losing our common language. Linguistic difference has destoyed or threatened to destroy several nations. Many immigrants are openly disloyal to America. Chinese immigrants are stealing our secrets and corrupting our political system.