I'm not sure I understand the reason for the change. Granted, 12 years after 9/11 nobody is going to be held at the point of a small knife such as those described here. But why does it make sense to allow them? I don't travel by air a lot; I've been averaging 2-3 flights a year in the past five years. Let's say I've flown 12 times since 2007. Not once did I wish I had a knife.
The attendant's union might be overreacting, but I think there is a danger here of underreacting.