The principled argument against the Arizona law

There is a principled argument against empowering the state to pursue otherwise non-violent, productive undocumented immigrants.  Unfortunately the left, immigration promoters and other assorted poseurs like the President find it easier to sneer and howl 'hate' than to make it.  Because it is founded on Liberty rather than State Impunity, I suspect that there are only a handful of leftists that have the capacity to think it.