While your first reason, catching the accomplices, is a valid one, although not for much longer, since they've obviously flown the coop by now, if they are going, the second one is not. It's not the Government's business to protect us from ourselves. We cannot take such measures, or support the proper governmental actions, if we do not know the facts.
What national Guard we have at home (still the vast majority of it) would be better employed ferreting out all the stealth Jihadies, and guarding them in tent cities pending their deportation hearings or trials. Start looking actively for folks who have overstayed their visas, and those who never had any having come over the border along with the economically motivated illegals. In the course of all that, you'd undoubtedly find lots of naturalized and a few native born citizens. They get full due process. The others get a hearing, with an appointed guard or reserve JAG officer representing them, before a civil or military tribunal. (Guard and Reserve JAG officers are almost to a person licensed to practice law in one or more states, and could easily be licensed to practice in the federal courts as well.). They get the one hearing, if the facts are not in dispute, they are put on a rusty tramp freighter for their homeland. Naturalized citizens get the same treatment after a full trial. Native born citizens go to jail or can at their choice be deported for life to the Terrorist supporting country of their choosing. (but only from a short list, mostly where we intend to invade shortly).
cue: crickets chirping.