The vast majority of illegal immigration to America is through a visa or green card expiring and not getting renewed, but you can't take a picture of that or make a sensationalist political headline with that. I'm a believer of making a nation more accessible to immigration as a way of increasing the labor force, and if people want to come over and work, we should provide a legal means for them to gain citizenship over time and make that process less obtuse. Some people would be afraid that migrants will take away jobs, but more laborers mean more demands for goods. There will naturally be jobs created due to an increase in population.
It also seems to me to be the right thing to care for our neighbors and give them a chance in this way. We espouse freedom of speech, freedom of markets, and many other liberties. Why do we take special exception to freedom of the movement of people? National borders are a practical necessity so that we can have clear jurisdictions over law, so that we can try to reduce arguments between neighbors, but do nations have the right to give or sell land away, as though we are selling people away like chattel? The idea of borders is a little silly. Of course I understand people wish to protect the sovereignty of the nation, however that so manifests itself, but often it comes in the form of xenophobia. And as conservatives are finding, Hispanic populations are actually more inclined towards conservatism in America, so they may find it in their interest to help, not hinder immigration from Mexico particularly. (I have no dog in the fight between the political parties. They are both not appealing to me and I am a political independent.).