Agreed. The only thing that he might have done differently to strengthen his position is to first answer with something along the lines of, "I'm just a hobbyist, I take pictures of whatever interests me". THEN if the cop had continued to push the photog could argue that he had given the cop the information he needed to do his job, and the rest could more easily be construed as harassment.
I wonder if that would be considered reasonably sufficient. Anybody (including that "terrist" the policeman is talking about) could claim to be a hobbyist. If the policeman then, having (as we should assume) reasonable grounds not to believe in this explanation, proceeded with his pushing the photog - could the photog argue successfully that he had been harassed? That's very much debatable.
Maybe not, but the point is, the photog could have given reasonable answers to reasonable questions rather than turning it into a confrontation right away. That would be my approach, anyway.
The issue seems to be in whether the policeman could have reasonably construed the photog behavior as justifying his (policeman's) "inquiry".
This is so subjective. I had been asked in an "insisting" manner by an employee of the kind of state archives building why I was taking pictures of it (from public grounds). My responses were not satisfying him. Situation was getting unpleasant. But I think most of people would agree with the policeman and that archives' employee.
I agree that there is a subjective component here, but the truth of the matter is that the photog's response alone may qualify as "suspicious behavior" in this instance. Candid answers like "I find the architecture interesting", "I'm testing a new lens", or anything that conveys that you are not worried about the cop just doing his job will get you a lot further.
Not long ago I was at my place of work over the weekend, taking calibration shots to send to the author of PTLens. The glass gridwork on the sides of the buildings was perfect for showing lens distortions. I was there for quite some time, as I have several lenses, a few of which are zooms and I needed to move around a lot to make sure I had good images with straight lines at the edge of each frame, lens perpendicular to the glass, etc.
Anyway, Security came along and eyeballed me -- then left without a word. They recognized me and my car and didn't disturb me at all. I expected some response from them even before I left the house; they were right on top of things. I brought my badge with me just in case. I think that with the 9/11 hysteria it's to be expected that you may be questioned when photographing certain subjects. It's a two-way street; it is the cop's responsibility to not presume guilt without reasonable cause, and it is our responsibility to respond to reasonable questions in a reasonable manner.
Another example; I went on a trip with two destinations before returning home. I had about 8 lenses in my carry-on. Leaving San Jose, no issues, not so much as a blink. Leaving Raleigh NC, the lady at the scanner said, "You have lenses in there... a LOT of lenses". Her tone was very slightly accusing, I just shrugged, smiled, and said, "that's right". Another TSA guy took the bag, looked inside, and did the little "swab for explosives" thing, then told me to move along. End of story. Leaving Pittsburg, the guy at the scanner asked if it was my bag, then said he had to look inside because "it looks like yo have a lot of camera lenses in there and they just look like black blobs". He went on to explain that he needed to look through each one, and when he had trouble getting the rear caps off(I have aftermarket caps with o-rings; they are a bit tight) he let me take the caps off each one, he inspected them, then I put the caps back on. Interestingly, they did not check the lens that was on the camera.
If I had been in any way belligerent in either NC or PA, the outcome might have been very different.
I am no more pleased than anyone else about the way we are shaken down like common criminals; I'm not even convinced we are safer for it. But I find that objecting on the spot is useless, better just to cooperate, not draw attention, and be on my way. I reserve my activism for letters to my reps, etc. where I'm not going to be strip-searched at gunpoint for expressing my views bluntly.
I am not even sure what I would like myself to happen in such situation, as long as it is not me involved.
(The above has nothing to do with the problems the policeman had with explaining his action and with the intentions the photographer could have in mind. These were the elements of poor education, low IQ, vigilantism, political bend, feeling of being a free, independent human, or feeling of being a member of a society, obliged to fulfill its orders in unquestioning manner.)