I'm not quite sure what he is saying is so irresponsible about it.
Is he suggesting that because people play at shooting enemies in a video game that takes place in the cathedral, they will seek out illegal guns in England with which to re-enact shootings in that same cathedral?
I mean, does he think that british criminals have nothing better to do if and when they acquire guns than to go and pretend they're in a video game? What would the criminals gain by shooting around inside the cathedral? Wouldn't they rather be out robbing people?