While useful, anyone's personal experience is usually far from being a sufficient condition for any serious analysis, and more often than not leads to the proverbial "not seeing the forest for the trees" syndrome. If opposite would be true, than any floor-trading stock trader would know more about economy than members of the federal reserve board (often academics themselves)... any paramedic would know more about medicine than university professors... etc.
Besides, as someone has already pointed out, "being in the same room or battlefield" with you disqualifies them as terrorists, at least those we in the western world should be afraid of.
And again, some of the key players in the 9/11 attack spent years living, getting high education and working in the West. Yes, they have a different value system, but stupid, idiotic and ignorant they aren't (unless, of course, you assume that not adopting our value system makes them so). Those who "never heard of soap" are not going to fly planes against us.
But just for fun, let's assume you are right and that they are really that stupid and ignorant... in such a case, they surely would not know how to operate a modern dslr, hence any photographer with a dslr should be automatically above suspicion... and only poor souls with Holgas and Dianas should immediately be arrested.
You're straw-manning my argument. We never defined "terrorist" so we are doing apples and orange comparisons all over the place. If you're mostly concerned about 911 style aircraft hijackers, then why are we discussing harassment of photographers on the street? And I never said all of them are completely stupid in the first place. Just that some are, and that it would wrong to think that they're too wiley to be caught with seemingly ordinary measures. Remember how the millenium bomber was caught crossing the border?
My point was, and remains, that there are a lot of people working very hard every day to stay one step ahead of any number of serious enemies. They take their jobs very seriously, and most of them are extremely good at what they do. There are also some over-zealous types at the fringes who do things like detaining wedding photographers. We can agree the second group are not helping, but that gives you no ability to make judgements about the value of what the first group is doing. Serious analysis by outsiders is compromised in this case by a very serious lack of facts.
Anyone who has ever worked inside a national security organization can tell you that their is a vast chasm between the public perception of what intelligence organizations do and what actually happens. The movies and the newspapers would have you believing some of the big US intel organizations are doing things daily which are physically impossible. There's a sort of running narrative that paints every last possible action in a negative light, and inexplicably ignores countervailing evidence that is staring everyone straight in the face.
Consider that most of what is publically known about intelligence sources and methods came from people who hate the intelligence community. Anyone with access to sources and methods takes an oath to never reveal them, and violation of that can carry the strictest penalties. So when a newspaper runs a story with supposedly insider information, it came from either someone who really doesn't know what they're talking about, or is a traitor. You may call them "whistleblowers" if you like, but consider that some of those whistles kill people. A few days after 911, the Washington Post ran a story that we were tracking Bin Laden via his satellite phone. Guess how long he continued to use that phone.
In the movies, anyone with a security clearance seems to be able to access any classified fact at any time. In the real world, programs are broken into small compartments with very limited access, to keep them safe. One individual may see only a small piece of the puzzle. Sometimes they're only seeing part of a deception plan, so if they go blabbing to the press, they may be saying thigs they believe to be true, but really are not.
Lest you worry that such a complex series of compartments promotes abuse, know that every single one is tracked down to the last dollar by congress. A long time ago, a number of politicians realized they could say pretty much anything they wanted to about intel people, because they knew the intel people couldn't publically disagree without revealing classified information. So now we have an arrangement whereby congress members frequently get briefed on a program, approve it wholeheartedly, then make public statements later that they didn't know, and are outraged. And the people who work in the organizations just keep doing their jobs in silence.
I'm retired now. But I'm still not going to let out the most insignificant piece of classified data. All I can say is that the threat is real. There are a lot of good people dedicating their lives to countering it. Some of them are highly competent, others are clueless. Same thing on the other side. The difference is that the good guys are generally so conscious of their duty that they won't even spill the beans when they're smeared in the most outlandish ways. The bad guys are so ruthless they'll cut the heads off reporters to make political points, use children to deliver remotely controlled bombs, specifically target civillian women, etc., etc. And yes, we still catch them from time to time because they do things you would consider senseless.
I'm sorry if you don't want to believe that, and I'm sorry I can't provide any more details, but that's the way it has to be.