There was a time when I was carrying in my bag a pair of medal numchucks (I had just bought them in a local shop) into the subway station. They were stopped by the metal detector and I was told that I either had to give them up or take some other form of transportation.
So yeah, China can be a bit over reacting when it comes to this kind of things. And if you think about, it may cause inconveniences, but it's not entirely a bad thing to the public, is it?