Well it was a replica of a gun. And it was large enough that if presented as such, a person could believe it to be a gun.
I have a real gun that is not much larger than 2". And I have seen real guns smaller than 2". I don't think the TSA guard acted improperly, in this instance.
If someone on the street used it to assault me, I don't think I'd have any problem using deadly force. Would any of you?