Some former Nazis have had their citizenship revoked for lying about specific actions in their past, but no one has ever had their citizenship revoked for exercising their Constitutional right to free speech. And how are defining an "enemy nation"? Any number of Americans went to N. Vietnam and denounced the war, as have others gone to Cuba and done the same. After WW2 a few citizens were jailed for collaborating with the Axis, but they kept their citizenship. You also are assuming the Arab MKs are naturalized citizens, some form of 2nd class Israeli, but in fact they most likely were born and raised there, with their family roots going back over generations. If such a vague notion as "breaking faith with the state" is to be the criterion, then whose citizenship will ever be safe? How will that be defined in the unforeseeable future?
Preliminary report: Palestinian stabs man near Damascus Gate, Jerusalem (Haaretz)
from the article: Conditional citizenship