We on the left have to make this a central part of our arguments, the starting point of our discussion.  Global inequality has to go.  We the poor of the United States have more need to make common cause with the poor super-majority of the global South than we do to exclude them.

Yes, higher wages and higher prices correspond to a higher standard of living.  More people who will work for less will drive wages down, and yes even television-stupefied overweight citizens would figure out how to do the work if paid enough money.  But as Al points out people denied all rights can be forced work for least of all.

Backing up largely-immigrant workforces already in the U.S. (let alone workers dealing with U.S. companies like Chiquita and Drummond Coal) can do more for everyone's standard of living than any wall.  And there is amazing organizing we can support already, from the just-formed-at-the-US Social Forum National Association of Domestic Workers to the Coalition of Immokalee Workers.

The problem isn't immigration, it's inequality.

And the only immediate answer is solidarity.