I can understand that argument, and I could make a good case for and against that point, but Mexico's best interests are not high on my list of considerations. Even if I grant that Mexico would be better off if we deported all the illegals(I don't), There are American economic interests and political realities to contend with.
We can both agree that illegal immigration is detrimental to America and Mexico in many ways, but it is shortsighted to believe that illegal immigration has no benefits at all. It wouldn't be tolerated if it didn't have benefits.
I believe illegal immigration is caused by arbitrary and unresponsive immigration quotas. These quotas cause a shortage of labor which in turn cause a great incentive for border crossings and unscrupulous business practices. The America birth rate is under sustainability levels. With legal and illegal immigration we rose only 1% in population last year. This limits our economic growth.
I think most American can agree that illegals who are drug dealers, gang members, welfare cheats, or just plain unproductive should be deported. Where you and I differ is the best method to solve the problem of illegals who are already here and future border crossings. I believe making it easier to enter and work legally from Mexico will reduce illegal immigration. I believe we should allow some productive illegals an opportunity to enter legally. Do they deserve it? No, but practicality is an issue. They are already trained in their jobs and there integration to American society will be easier.
Dubya's guest worker program will make finding unregistered illegals easier by eliminating the need to find illegals who have registered. Deporting the criminal and parasite illegals is unlikely to make things better for Mexico but I prefer them in Mexico.
And massive immigration isn't making anything better at all.