Why people would fight over languages?

Why people would fight over saying that only 'x' speakers can be here, 'y' speakers are invaders, are alien. Come yrr, we all live in a united country, and we all have the right to be anywhere in it. If you get so insecure about your language, than the day won't be far when we will actually need visa-passport to travel. You can reduce the influence of other languages by practicing your language, rather than imposing and alienating other languages!