Having a huge class of illegal immigrants allows employers to exploit a source of cheap labor that has few socially recognized rights. The solution isn't to deport them all, which would be impossible, break up families, and destroy our economy, but instead to legalize the immigrants. Yes, some of them came in violation of our laws, but 99% of them came because they were having trouble surviving at home, and there is no crime in doing what it takes to survive. Immigration will continue from countries with low wages to countries with higher wages until the global distribution of wealth is more equal. Immigrants accelerate that equalization process through their remittances.
Bottom line: if you couldn't find a job here and you heard there were good jobs in Mexico, you'd do anything to feed your family. That's why people are coming here. There's nothing wrong with that. There's something wrong with a system that labels them criminals.