1. Banning objects doesn't work. If people get a mad on and decide to off some folks, nothing is going to stop them. If they can't get a gun, they'll make a bomb. If they can't get a bomb, they'll run amok in a classroom or train car with a cooking implement. It's a punk's game and you can't win it.
2. Group punishment is not something that applies to free adults. Unless you are in Cell Block D, Mrs. Krabapple's third grade classroom, or Recruit Training Platoon 101, then punishing, penalizing, or in any way inconveniencing Person A for the malfeasance of Person B is a BS non-starter, okay?
3. Lastly, contrary to the maundering of that idiot Limey poet, I am an island; get it? There are quite literally billions of individuals on this planet whose demise would not diminish me, (or you, for that matter) in the slightest. If anything, going into spasms of hand-wringing and what-shall-we-do? over the death of someone you never met and never would have met actually strikes me as a little disrespectful to the people who actually were diminished by their death.