Police chiefs in Arizona and around the country believe that Arizona's anti-immigrant crackdown will lead to an increase in crime. That's no surprise. Aside from the fact that the supposed positive correlation between immigration and crime is mostly mythological anyway (indeed, if anything immigration is negatively associated with crime), the folks who actually are interested in committing violent crime are no doubt thrilled to know that the police will be wasting their time on trivialities.
Meanwhile, anything that increases distrust between immigrant communities and the police means that crime is less likely to be reported, that information that does come in will be sparser, less reliable, and harder to track down, and in general the job of cops policing immigrant-heavy communities will be made that much more difficult. But hey, what's the point of having baseless prejudices if you can't use them to enact policy?