I don't see what the practical point of kicking out illegal immigrants is. Almost half of them immigrated legally anyway, and almost all of them with the same aims that legal immigrants would have had. Like OK it proves a point by enforcing the law I guess.
Its never a good thing to have a population that can't go to the police for help. That's how you get second class citizens, and that's how you get widespread victimization. If an illegal immigrant dies because they weren't willing to seek protection from the cops, or they didn't have health insurance to seek preventative care, that's not a win. That's a loss in my book.
These people would have been let in anyway under a sane system, the difference is they would have left. Tighter border controls over the past 60 years resulted in people who would have come and left on temporary visas just... staying. The demand is there, now its filled by undocumented workers rather than documented ones. The thing is, mexican immigrants fill an important role in the US economy and society. The US population growth rate is 1.88 births per woman. The average lifespan in the US is 80 years, so that means that over 80 years we need (1.88/2 (percentage of population loss without immigrants over ~80 years) * 320 (population of US in millions) /80 = .2) 200,000 immigrants per year to maintain a stable population. We allow 500,000 legal immigrants per year (we naturalize about the same). BUT, the norm for the world is a population growth of about 1.11% per year, which for the US would be (320 * .01) ~3.2 million. Meaning that we need 2.4 million illegal immigrants, or if all illegals were deported we would need 2.7 illegal immigrants to maintain average population growth. And as people have noted, migrant works and illegal immigrants fill a different economic niche than the average American.
(if my population statistics don't match up: remember. Baby boomers were born baby 40s to 60s and account for 20% of the population. Birth rate dropped in the 70s. Sometime, the boomers are going to start dying off and then things will get real interesting)