If undocumented people are paying taxes, it's usually because they stole someone's documents to get through e-verify. I think there's a lot of people who are willing to whitewash the truth about the problems that go along with illegal immigration. Now sure you could certainly take the position that we should just hand out legal status to anyone with a pulse who wants it, but that's not really a fair system either, nor is it one which most countries can reasonably have.