There we have it....... two words and a succinct explanation
existential threat
Yep. If Obama gives in to banning one group of foreigners, even temporarily for life and death health reasons, he’s then let the Camel’s nose under the tent for restrictions on other groups down the road.
The issue is somewhat parallel to partial birth abortion. Once the left allows a ban on nine month baby killing, regardless of how horrific the practice, it then creates an existential threat to their entire abortion argument.