In a nation that now relies so heavily on consumer spending to support its standard of living, every business and government institution has a vested interest in importing new customers -- regardless of where they come from and what their political/cultural defects might be.
Keep in mind that a 25 year-old who crosses our southern border illegally without a penny to his name is actually a better "prospect" for this country than his American counterpart who has unrealistic expectations in life and (often) a negative net worth due to excessive college debt.
True, I have had very good relations with people I assumed to be illegal, and tend to like them in general. This is why throughout most of our history we have turned a blind eye to them, in smaller numbers they were seen as a boon to the society at large.
We aren't only talking about Mexicans, but Canadians and Irish as well, used to be able to move freely in and out of the country. In a way, I miss those days.
But still, if you are elected or appointed into government, your job is to represent and protect my interests.
And when people are coming in, in numbers passing 2 million a year, citizens should have something to say about it.