I think Megan McArdle gets the racial angle about right in these two posts:
The people claiming that this is somehow not about racial profiling seem, quite frankly, to be living in some alternate fairyland universe where police are going to rely on their psychic powers to peer into the minds of the people they encounter, rather than relying on external signals like . . . skin color. [ellipsis in original]
...Perhaps uncharitably, I think that the people who supported this law are not overbothered because they're not the legal citizens whose skin color just became "suspicious." Yes, again, I understand that they have legitimate concerns. But I just can't believe that they would think that this was a proportionate and sensible response to those concerns if they themselves risked being held in the pokey until the police could check their immigration status. The reason this law passed is that the people who support it--the same people now claiming that this isn't about racial profiling--know that it only applies to people who are poorer and darker skinned and probably speak with funny accents, anyway.
I'd be a lot more sympathetic to this law, in fact, if it required the police to check the immigration status of every single person they pulled over, without any gauzy "reason to believe" fig leaf to cover up what's really going on.
Raise your hand if you think that law could have passed in Arizona.
And
The folks arguing against my alleged accusations of "racism" on the part of Arizonans are missing the point. I didn't accuse Arizona of racism, and I have no idea whether they are racist or not. What I do know is that majorities are usually markedly less concerned with the infringements of liberty that they expect will only happen to other people. This is not racism, it's human nature.
If the immigration problems in Arizona are really so serious that they merit deep intrusions upon the liberty of citizens who happen to resemble illegal immigrants, than they are serious enough to intrude on the liberty of everyone. Don't make the cops check the status of anyone who they "reasonably suspect" is illegal; make them check the status of everyone, no matter how blond-haired, blue-eyes, and fluent in standard American english they may be. If you forget your license at home, the police detain you, just like they detain anyone of mexican descent, while someone fetches it. If you can't produce a birth certificate, passport, or similar, then you wait in the pokey until they can verify your legal status. No police discretion. No profiling.
If it's legitimate to do it to them, than it's equally legitimate to do it to you, if for nothing else than the benefits of social cohesion.
If, however, this law could not possibly be passed if it affected the majority, because it's far too intrusive and would result in a lot of people passing unhappy hours in jail or waiting by the side of the road while the police checked their ID with immigration . . . well, then, it's probably not something we should be doing to other people, either. [ellipsis in original]