Sure, in a situation like this large public gatherings are not too safe - if terrorists are on the loose. But some of us Americans live in large cities and end up in large public gatherings say like in NY. If the "authorities" cannot protect a large group of people at a heavily protected location they are not able to protect any large group.
I leave the defense of my family, my person and my possessions to my self.
Good for you. And you have apparently decided that I'm against such a stand, which would be absurd.
FYI, I work maybe a mile from the Pentagon, so I've got a pretty good feel for the threat.