Way too much emotion and hyperbole on this issue.
Obviously, you can't simply take away gun rights from someone for being on the current watch-list that we have. A higher standard must be established, because the current watchlist is an amalgam of a number of law enforcement methodologies, bureaucratic record keeping and poor investigative techniques...most of these shortcomings being related to insufficient resources to monitor such large numbers of people. So a standard that is so large and unspecific is not a good tool for limiting access to firearms. That said, a standard can be established with a much higher level of scrutiny...there are currently more than a hundred active investigations into terror connections, in all 50 states, and likely hundreds more that have been conducted with "inconclusive" results. That is the target group, or it should be, for the kind of weapons ban we are talking about. Making a ban inclusive of persons under "reasonable suspicion" of "foreign" terror ties, and establishing strict guidelines for how the FBI would determine who fits in that category, is a more nuanced and effective way to limit the access such people have to heavy weaponry.
Mr. Trump's biggest weakness, and I say this as a supporter, is that he blurts out non-specific concepts such as limiting access to weapons for people suspected of terror ties...a point that is not wrong but is so vague as to create valid concern that such an approach could be abused and become tyrannical. As time goes by, his approach will refine itself into something like I've asserted above...so while I understand all of the concerns on this topic, they are unwarranted. Even if Mr Trump wanted to put in place such a broad restriction, it would fail to survive even the more liberal courts in the nation. He will out of necessity have to narrow the scope and focus of his restrictions....but at least he has the will to do that much in a way that focuses on foreign terrorism within the U.S. and will not, as Mrs. Clinton/Obama strive to do...seek to limit access to guns for the entire nation.
