A terrorist who is smart enough to be one does not need to dress or look like one. (Eg, would osama look like osama when he goes to washington to visit his comrades?) She may look like an auntie from Poland, shoot with mini spy cams all over her as she make stops to adjust her bra straps or pantyhose. When 911 happened, all the security measures did not stop the bad guys, even at highly guarded areas. When I travelled to usa, sometimes i wonder who would be seated next to me and whether he/she is on a suicide plane mission. But I have been safe so far fortunately.
So, that goes to show that when one is stopped by a guard or police for questioning, the photographer should forgive the guard for not receiving the proper training to detect real threats. Give him a polite smile and thank him for his little part of vigilance to make this a better place. Main thing is, praise him and quickly walk away with the pictures that had already been taken.
That being said, over reaction is better than none. We should instead be thankful we are living in a safe country lor.