On the Slippery Slope we see going on right before us:
On a hundred-year time scale you have more to fear from an unaccountable government than you do from radical Islam. A bureaucracy empowered to place you on a list where your rights can be excised or suspended will follow the inevitable path of all government agencies and programs: its scope will grow, it will become more opaque and resistant to oversight, and it will resist reform at every moment. Islamic terrorists have signifiers, tells, and structures we can attack with either our intelligence services or military options. Government agencies are nearly impervious to all forms of challenge.
Just look at the Congressional investigative attempts over the the IRS in the TEA Party targeting or the State Department over the Benghazi inquiry. Agree or disagree with either issue is NOT the issue – it IS about agencies that refuse to acquiesce to their lawfully (and Constitutionally empowered) overseers.
The list that denies a potential terrorist the right to buy a gun today may expand to animal rights activists or Black Lives Matter protestors or anti-abortion campaigners tomorrow, all depending on the whim of the executive or even some a nameless bureaucrat. A list that stops you from boarding a plane today is a list that might deny you a license to drive, speak, or vote tomorrow.
-Rick Wilson (The Federalist)