Is it going to be a blanket excuse for racial profiling? Probably. But does it have to be? No. Arizona could defuse all accusations of racial profiling by randomly and persistently asking people of every color to prove their citizenship. And for border states, I do not think this is necessarily so wrong.
For example. Once upon a time I was seeking three housemates for a house I was renting in Arizona. I found three really cool people, pretty quickly. Probably the most decent and responsible among them, and the promptest with the rent, was a tall white guy I will call S. After he'd been in the house for a few months, I learned that he was an illegal alien--from CANADA mind you, not from Mexico. He had no difficulty finding under the table work in Arizona, in fact he was a popular employee because he was punctual, literate, civilized AND hard working.
I did nothing when I found out he was an illegal. I liked him, he was a good housemate. After a few months passed, he asked me to participate further in his subterfuge by registering his vehicle in my name. I refused. A younger and sweeter housemate agreed to take responsibility for his car. After that he didn't ask me for any more favors along those lines.
After some time he began dating a friend of mine. They were really in love. But his lack of citizenship was an issue. It was always going to be an issue. No matter how hard he worked, he could not overcome it. He was afraid to go to the authorities because of how they might treat him. So he did not. Eventually that relationship ended, badly I might add, and he ended up back in Canada. No harm done? Debatable.
So I guess my point is that just being brown in Arizona is certainly an additional risk for being harassed by that aggressive Sheriff, but we need to consider ALL the illegals and ALL the citizens with our laws, not just the ones of a particular color. And we need to have compassion for the illegals, at the same time that we need to have some rules about who is permitted the rights and responsibilities of citizenship. And there are responsibilities as well as rights, in my view.