Yeah, they're just like their globalist free trade brethren...it's all about lower prices.
Lower prices are beneficial to us all, cheaper wages mean that we all are richer from more abundent goods and services. The problem is two-fold, but it isn't that Mexicans are "stealing jobs." No, the real problem is that our government has placed so much tax and regulation (especially the minimum wage) onto Americans that black market foreign workers are needed to fill economic needs. The other major problem with these illegal aliens is their nature, namely that they are illegal aliens, flouting and cheapening our law while at the same time doing little to aculturize into Americans. I have no problem with cheap wages, indeed we should abolish many taxes and regulations so wages can be legally lowered for everyone, nor do I have a problem with immigration, just the failure of American policy to turn these immigrants into people with American values.
There is also an issue of these immigrants sucking up vast amounts of public goods and services (read welfare\health care, etc). Of course this wouldn't be an issue if not for the Unconstitutional network of government mandated charity (read theft). In any event, the consumption of American taxpayer funded services amount to a massive hidden cost for these workers. Those individuals who think that they're getting a good deal from illegal labor from foreign nations are simply dilusional.
While there is no easy solution to this problem a good few steps in the right direction would be to freeze the border, seek ways to reverse intensive government charity activities, and to amend the Constitution to require that 3 out of 4 grandparents have been citizens in order for a child to be born a citizen. This amendment would revoke citizenship for anyone not meeting those requirements at the time of its passing.