I have issues with anyone who could sign a bill saying it's ok to stop someone and demand papers based on visual evidence, but not be able to identify what visual evidence is.

There are people who feel that this bill basically says "If you look like someone who could potentially have come from Mexico, you are legally required to carry I.D. at all times."

If you had a bill that said:

All Residents of Arizona over age 16 (or 18 or 21) are legally required to carry government issued identification and may be asked for this identification by police at any time.

People would be screaming police state, and opposing the bill en masse.

Yet when you put the visual language in it seems to read:

All Hispanic residents of Arizona who look like adults are legally required to carry government issued identification (e.g. papers) and may be asked for this by police at any time.

I think the evidence of this is seen by the press conference after the Governor signed the bill into law. When asked "What does an illegal immigrant look like" she had no good answer. I can't imagine someone would sign into law a bill that allows visual identification without understanding what that visual identification is, and to me that means dodging the question.