Normally you figure that law enforcement officials care about...law enforcement. Apparently that is not true. Here is a story about a North Carolina sheriff who opposes immigration reform. He claims that it does not do enough for enforcement, but you dig slightly deeper and see the real reason.
Of the bill's provision regarding a pathway to legal employment/legal status, Page said the National Sheriff's Association takes the position that "under the conditions and provisions of a guest worker program, persons here illegally must come forward and delare [sic] themselves to the United States government. The illegal individuals can then take the steps necessary to achieve legal status under a guest worker program. Under a guest worker program, U.S. Citizenship cannot be obtained."
This is problematic. First of all, at what point did the official positions of sheriffs center on citizenship rather than just law enforcement? Second, if they did think there was a link between citizenship and crime, then they should be aware that naturalized citizens commit fewer crimes than the native-born. As I've argued before, the crime problem is not about immigrants per se, but rather immigrant assimilation into a terribly violent and often unhealthy culture in the United States.
In short, this view is both uninformed and is very likely simple racism. We don't want more of "them" because based on my narrow views, "they" are dangerous and I do not want "them" around.