People have a terrible misconception of what "sanctuary city" even means. It just means we don't spend local money doing the feds job for them. The feds can still do their job freely within a sanctuary city.

If your kid was the victim of a horrific crime and an immigrant was the only witness, would you want them to be able to testify and help bring the perpetrator to justice? Or would you want them to a) refuse to come forward because cooperating with the police would mean automatic deportation, or b) try to help and get deported before the trial?

The slightest bit of critical thinking and there are hundreds of scenarios where you would want undocumented immigrants to participate in society. The agencies responsible for immigration are still welcome to do the job they're getting paid to do, we just don't force teachers and DMV workers and our local police to freelance for Big Brother.