Sanctuary cities by definition hide criminals. Sanctuary cities by definition shield felons from federal law. Every democrat who supports sanctuary cities has made it clear that they will make no effort to vet the origin of the foreign criminals they aid, abet and support. Some or all of the foreign criminals that democrats are paying to live in sanctuary cities could be terrorists, rapists or murderers.
Sanctuary cities = rape
Sanctuary cities = murder
Sanctuary cities = terrorism
Given that no one can vet the fake refugees coming out of places like Syria anyway, barring them from entering the US is the only rational position unless you are deliberately importing terrorists into the US. Democrats are therefore, in my personal, political opinion, the party of treason and the party of terrorism.