The fly in the ointment is that it is assumed that people of 'Mexican appearance' will be the targets and, if legitimate, will, possibly inconveniently, have to carry the relevant papers which the liberal left are unilaterally declaring to be: unamerican, nazi, racist, 'not the done thing' etc, etc.
(Not too far off a limited version of Labour's failed ID card system here, really.)
So certain 'liberal' states are now in the act of 'boycotting Arizona' - apparently with the aid of Obama himself.
What has troubled the people of Arizona is the high crime levels from the illegals and most unreasonably, they wanted this stopped, all previous feeble efforts having failed miserably.
Now here's the rub. SEVENTY percent of the electorate voted for this measure!
Let me summarise then. We have to balance off the democratic wishes of the people against a relatively minor inconvenience to the legitimate gastarbeiten.
So, under these circumstances, according to the liberal left: DEMOCRACY MUST BE IGNORED BECAUSE IT CONFLICTS WITH THEIR OPINIONS!
They terrify me!