It's amazing that there are people who actually think people on terrorist watch lists should be allowed to buy guns
Yup. As I've said elsewhere, if it's proper for the government to say that a person who has psychological problems can't purchase a gun (and I don't think anyone argues against this), why wouldn't it be proper for the government to say that a person who has been placed on a terror watch list can't purchase a gun?
Plenty of people, including myself, believe that psychological problems should not of themselves be enough to keep someone from legally purchasing a gun. We shouldn't be depriving people of things merely based on a diagnosis.
I don't think being on a terror watch list should keep someone from being able to buy a gun, first because that means depriving someone of something considered a right without due process. If there were more of a limited process of putting people on this list, then perhaps, but there's also the problem that it would alert the person that they are on the watchlist and - if they are of that tiny percentage of people on the watchlist who are actual terrorists - they would find another way to kill people instead. If they are on a watchlist, you want to watch what they do.
This guy who shot up people in Orlando was not even any longer on a terror watch list when this happened. But if it's true as been reported that he had been guilty of domestic violence and threatening people in the past few years, I think that should have been enough to keep him from getting a gun.