The vast majority of the illegal immigrants have come here only for economic reasons. They have their own culture which they like just fine and vastly different from ours. (If you want some proof, go watch "Y Tu Mama Tambien" playing in a theatre near you).
As a nation, Why do we want to bring in vast numbers who do not hold things such as the constitution and its bill of rights sacred?
The push for liberal immigration laws comes in large measure from those who want to destroy each people's sense of their own identity. It is part of the pursuit of an undifferentiated humanity. For the basics of this mindset, you might consider
Myths & Myth Makers In American "Higher" Education, noting that the first section, which deals with Lord Keynes has to do with economic myths; but the rest is in point.
William Flax