I hate to go straight to Hitler, but there's just nowhere else to go.
The Arizona state legislature has declared that police can demand to see documents from anyone that might be an illegal immigrant. If you don't have your proof of citizenship or a proper visa? You go to jail.
If you don't like being compared to the world's most notorious fascists, maybe you shouldn't make laws that allow you to round up different looking people, demand their papers, and throw them all in jail.