"Having a highly developed society and culture. 2. Showing evidence of moral and intellectual advancement; humane, ethical, and reasonable: terrorist acts that shocked the civilized world. 3. Marked by refinement in taste and manners; cultured."
Here's the thing. Some nut tries to blow up a plane with his shoe or underwear and we do all kinds of things to try to prevent it from happening again. From 2005 -2015 we've had over 300,000 gun deaths. The equivalent of over ten 9-11's. Yet we do nothing. Zippo.
Even that late great liberal (😀) Supreme Court Justice Antonin Scalia said in the Heller (5-4) decision that individual states and the country as a whole can put limits on the Second Amendment.
In other words the Second Amendment is not limitless. For example you cannot own a bazooka or a tank. So, if the country wanted to we could ban these type weapons that can slaughter large crowds of people in a few minutes. We choose not to.
Most gun owners are for common sense gun safety laws like enhanced background checks etc.. Yet we can't even get something like that passed.
A small minority are keeping the majority from moving to where the rest of the 'civilized' world is regarding guns. So, the slaughtering will continue unabated.