This is so overblown it's ridiculous. This law is being used, cynically, by those forces who want illegals to be able to stay here and be citizens (or quasi-citizens) with no repercussions. It's simply a political power play, whipping people up into a frenzy.
The Arizona legislature has clarified that this law is only intended to allow police to check residency status of people they detain or arrest. And appearance/race is not a reason for stopping people.
"Lawmakers on Thursday night changed the language to require scrutiny only of people who police stop, detain or arrest. They also changed a section of the bill that barred officers from "solely" using race as grounds for suspecting someone is in the country illegally; opponents had argued that that would allow race to be a factor. The legislators removed the word "solely" to bar race from being used by officers enforcing the law."
This is not Nazi Germany where you have to carry papers everywhere you go. However, if you are stopped or arrested in Arizona, you may get your residency status checked. Why is that such a problem? The police can check every other freakin' thing about you, and if you have any outstanding illegalities on your record, they will process them on you. Why not this one?
Because the thrust of the protest against this is that being in this country is NOT illegal and should NOT be used as a basis for denying people services or deporting them. Why do you think they are trying to push the term "undo ented"? Because it implies you're just missing some silly do ents, and you should have all the rights and privileges of being here in the USA. They are also trying to make it a "human rights" issue.
Don't be fooled. You are being spun by all these news stories and protests to believe that illegals should be given everything we have and be allowed to stay here with all rights and privileges.