A quote:
In 1986, when there probably were 3 million to 5 million illegal immigrants, Americans accepted an amnesty because they were promised that border control would promptly follow. Today the 12 million illegal immigrants, 60 percent of whom have been here five or more years, are as numerous as Pennsylvanians; 44 states have populations smaller than 12 million. Deporting the 12 million would require police resources and methods from which the nation would rightly flinch. So, why not leave bad enough alone?
People are not annoyed because they are racist. They are annoyed because they are being invaded. The fact that this particular invasion is not lead by an army is irrelevant. Whole piece at WaPo here.