Most airport/railway workers, or for that matter police officers, cannot recognise the difference between a "professional photographer", a "criminal photographer" or an "hobby photographer".
So because of their inadequacies Joe Public is prevented from going about their law abiding business? Isn't that effectively surrendering our basic freedoms to the terrorists? I guess they're winning the war then!
I have no problems with an i/d check, but I do become agitated if some ignorant job's worth tries to move me on when I'm on public property engaged in a legal activity.