This mischaracterizes what sanctuary cities are. They do not protect undocumented immigrants from criminal prosecution if they commit crimes. They prevent them from being arrested solely for their immigration status if they’re in the process of REPORTING crime. For example, an undocumented woman could report having been raped, without fear of being deported for simply reporting a crime, if her immigration status is her only offense.
This is for safety reasons, and ensures that everyone – regardless of immigration status – can engage with law enforcement safely when necessary. Hamilton’s recommendation here would destroy Sanctuary cities, making them a thing of the past, and make it impossible for undocumented immigrants to report crime for any reason. That’s definitely NOT what you want, and is almost certainly in service to their “round up all illegals and deport them” ethos, which would have devastating humanitarian as well as economic38 consequences.
Full contextual analysis of Section 3.8: Department of Justice here.