You're not answering the question at all. Being an imperialist power and oppressing other people is good for you as a society if you win (just ask the British; they're still enjoying the fruits of their imperial policy after all this time), even if other people find it morally reprehensible. This doesn't equate in any way to believing that accepting immigration is helpful to the society.

Just look at modern-day China: the Han Chinese ethnic group dominates, and oppresses all the minority groups. China is not a country with a lot of immigration either (nor do they have a shortage of people). So far, it seems to be working out for them, though admittedly it sucks for the minorities.