Well, a couple of thoughts in reply:
First, the mechanics and actual implementation, such a list of what is / what is not dangerous is silly because that is what happens when one writes down a list to select items in the first place. But that is just a nuance IMO and does not change the bigger picture, and there really is not a functional way around it. Without an outright definition or list in this case, we end up with "I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that" - Justice Potter Stewart, US Supreme Court. Now, do we really want a gazillion TSA agents deciding what is dangerous without a list but simply 'knowing it when they see it'? Not me, I like my rules written down.
I believe your comparison of current security levels vs. pre- 2001 levels and the results are fundamentally flawed because while a very specific method was used on 911 and it would be easy to stop that (we are in agreement here; reinforce the cockpit doors and be done with it), the larger picture is that the entire terrorist world, domestic and international, was schooled on how easy it was to access commercial aircraft for terrorist acts. So the exact plan of 911 is stopped by an armored door but that would just drive someone two steps to the left to commit other terrorist acts, in a slightly different way. So you cannot view a large problem such as terrorism, sight one example, propose a cure for that specific example and claim that overall terrorism would be reduced IMO. Want an example? After hardening access to all planes cockpits, a terrorist could buy / steal / make an airline worker's uniform and hang a library card from a neck band (to serve as an Airlines ID- who looks anyway) and put 50 lbs. of high explosive anywhere on the plane, the easy way being in plain sight as baggage. How about grab a USP truck and uniform, fill it with explosives, and drive it to a terminal as close as possible. The point being that if you have a ship full of rats and find out exactly where they are getting into the ship, closing that port will do not good as the rats will simply use another hole, so a practical approach MUST involve a general ship tightening...... or what we could call general increased security to be effective. The degree of security is negotiable but the underlying principle holds. So addressing the cockpit access would not be sufficient IMO and would do nothing to address the larger problem of airlines and terrorists, merely steer the culprits from one very specific method to the many (infinite?) others available.
The other side of the same coin is to say that if a determined person or persons are going to commit some crime, there is nothing that will stop them, and therefore any security is pointless. So a car or motorcycle model having very high theft rates might as well forego any and all security measures, starting with locking it, because it will not work anyway. It seems logical but is incorrect because the percentage of thefts will increase as security drops off.
Now the final part of your post is the most interesting to me, the most dangerous to speak about and the one that cannot be employed. I believe you are speaking of risk / reward, or cost- benefit ratio. I am a fan of this myself and apply it often but not so much out- loud 'cause of all the incoming bricks, people gathering with torches and pitch forks, etc. It actually starts with indisputable facts that also cannot be stated: if you have aircraft flying around, you are going to have plane crashes. If some of those planes carry people, some of those crashes are going to kill some of the people who fly. It cannot be prevented. This applies to cars, firearms, electricity..... look up bucket drownings for an extreme example. We can reduce the incidents of mishaps and we can reduce the levels of injury on average (seat belts, air bags for example) but we CANNOT eliminate them. But with things such as air safety, we want zero deaths. It ain't gonna' happen but we cannot state it otherwise. Now the tough part: reducing the death rates costs something, and as no one and no entity, no matter how large, has infinite amounts of resources, some amount of deaths must be tolerated, expected, and 'allowed' to occur. We use cars everyday, we have auto deaths everyday and we quietly (because we cannot talk about it.... torches and pitchforks and all) accept it as a cost in the cost to benefit ratio. We have determined that a balance of circa 40,000 auto deaths in the US per year is an acceptable price to pay for the benefit of all of us having the use of cars. But it cannot be stated that way.
The same thing applies to everything but gets even more socially unacceptable to be stated: airlines, for example, and some types of cancer jump to mind. Trying to find an acceptable balance between security and terrorist deaths is readily doable but cannot be implemented because it is distasteful and totally unacceptable as a method to our society. Child cancers are extremely rare and so get a hugely disproportionate amount of money, research, time and effort, along with a hugely poor cost to benefit ratio but who could possibly suggest cutting back on any of this would be promptly burned at the stake. Cancer in children is quite tragic and really pulls at the old heart- strings of just about everyone (myself included) and so we allow emotion to make what are really straightforward, logical decisions. I believe this is not possible to 'fix' and so we will have to live w/in these restrictions forever: Airlines MUST be 100% safe, with all partied, the Gov't, the airlines, the airplane manufacturer, etc. etc. responsible to prevent ANY accidents or other acts that would cause deaths. And when those deaths do occur, as they always will (uh- oh, mob forming outside) we must absolutely pummel, punish, disgrace and basically terrorize anyone / everyone involved with that flight. Same thing with medical mistakes (honest mistakes, not fraud, etc.); we will not accept that they happen, will always happen and so go to excessive lengths to eliminate them, which of course cannot be done.
Brian (in his non- fun, not light or amused mode)
It would certainly be political suicide, but I am not sure about reckless
The second portion of that is more like a straw-man argument.... The first part I will address. I would increase security based on actual prevention. All this crap started 9/11 and the main reason? Because the doors on the cockpit were not strong/secure. Yes, it might be an oversimplification, but I think it mostly boils down to that. Restrictions on lighters, toenail clippers, tiny quantities of toiletries, blunt butter knives, baby food, shirts with Arabic writing on them, and micro-nude scans are absurd. Couple that with a "secret" no-fly list that no normal person can query or challenge, and you throw the Constitution right out the window.
It depends on what people find acceptable. If never having a single plane EVER go down due to security- that is probably just impossible. And if that is the goal, then ridiculous amounts of security- hundreds of times what we do now, will make no difference. It will just make air travel nearly impossible. Ban all carry-on, require everyone to be strip searched and then put on jail uniforms, and be handcuffed to the seats during travel; but what about the plane staff? The maintenance crews? The baggage handlers? The security agents, themselves?
It is not as if anyone is going to listen to me, anyway
I think that mostly the levels of security we had before 9-11 were reasonable, just add some fast technology upgrades. You could get through security lines in 5 minutes. Remember, current security which is WAY overkill and invasive has been shown to be 95% ineffective. So, theoretically, if we cut out 95% of what was introduced by 9-11, we will be no worse than before. Being told to arrive TWO HOURS before a flight is just insane! Add that to all the traditional headaches: the drive there, parking, late planes, delays on the runways, missed connections, lost or damaged luggage, and it is no wonder people are avoiding flying as much as possible and the entire industry is hurting badly.
It is the thoughtless ranting that brought on the extremely expensive, 95% ineffective, and unacceptable security we have now. "Save the children!!!" We responded emotionally, not rationally, not with science, to the situation. But you are right, it is complicated. I am not a travel security expert, so I don't know exactly what best approaches to use, but what we have now is obviously not the best approach by all kinds of measures including results, timeliness, cost, privacy, and convenience. I have had direct experience with the "new" security theater several times now in airports and, to me (and many others), it is unacceptable- if for no other reason, the slowness. At least some of the most insane security measures were cut back over time, but only after pissing off millions of people for too long. If bombs are the main concern, then focus on rapid chemical detection technology and give all the rest of the stuff a rest!
And the REALLY crazy thing is that all this focus on planes, which only carry a few dozen to a few hundred people- the terrorists can and will just switch to one of a zillion other MUCH easier targets instead. Malls, sporting events, interstate roads, libraries, schools, hospitals, churches, trains, buses... we can't secure everything everywhere due to irrational fear. And when we try, the terrorist have won- they have destroyed freedom and instilled terror.