There are the reasons people, especially partisan politicians, give and the real reasons.
Watchlist has imperfections and possible violation Second Amendment rights were the reasons used by the Senate GOP. What list is perfect and shouldn’t the SCOTUS determine constitutionality rather than the Senate? A Real reason omitted is fighting terrorist is a top priority of the 1%, in order to protect their assets around the world, while gun violence is not a threat to their assets. Pandering to the NRA, firearm company investors and dividing Americans politically, add to the undeclared reasons.
A consequence of the GOP’s No-fly List Gun Debate position is to enable the terrorist’s stated goal of dividing Americans, politically. Perhaps a top 2016 election issue should be, which of our two political parties is our terrorist enemies’ Most Valuable Party (MVP)!