Packy Anderson wrote the comments below on his Facebook page, and gave me permission to repost them:
I'm glad I don't have to go to Arizona anytime soon; I'm not sure if my passport is up to date. I'm descended from illegal immigrants, and I could easily pass for a native of Ireland. If I can't prove I'm a citizen, they could arrest me.
The AZ law requires police officers to question a person about his or her immigration status if there is "reasonable suspicion" that person may be illegally in this country. That's a particularly vague wording, and it gives a police officer carte blanche to question anybody they can concoct a "reasonable" rationale for. If I don't happen to have proof of my citizenship on me, then I'm subject to arrest. The only thing that can assuage my fear of being arrested without cause is the knowledge that I don't fit the racial profile the law was enacted to target, and that's not much comfort. So, until AZ changes it's law, I need to carry a passport to move freely without fear of arrest within a section of the country I'm a citizen of.
I go through life with the assumption that if someone CAN abuse the power they have over me, they WILL. This is a nation of laws, and unless the law guarantees that the police are not allowed to treat me in a particular fashion, I have to assume that they will. And I also assume that if the police are likely--or required by law!--to treat any other law-abiding person in a particular way then I am also going to be treated in the same fashion.
Finally, of course, a lot of it comes down to my personal religious faith. The man I follow once said "whatsoever you do to the least of my people, that you do unto me." Sure, I'm not an ethnic Mexican trying to make a living surrounded by people who despise me because of my ethnicity. I'm also not old enough to remember the days when my great-grandparents couldn't get jobs because workplaces had signs hanging outside saying "Irish need not apply". But if I don't care about such things with my entire heart and try to change them (and, since this is a law in a state I'm not a resident in, the most I can do is speak out against it), then I'm doing these things to my saviour.