Oooh, did I see another philosopher in here? It's interesting to me to see how many people haven't gotten past the deconstruction stage of philosophy, and don't possess the logical rigor necessary to construct a consistent opinion, and yet believe that they can state something is incontestable or absolutely true. You've got another think coming. Seriously. Anything is contestable (obviously). An inability to see past your own preconceptions is the only thing that would lead to a claim that something is self-evident, without any actual argumentation. Having taught philosophy for several years--if you're going to debate ideology, at least do us the courtesy of PROVING your argument with something other than "I don't live in a fantasy world, Ideology is everything." That kind of argument receives a failing grade in my course.
I actually think this thread has spawned some very interesting comments, although it's amazing how far afield some people have gone. I mean, seriously, at least TRY to keep your comments on topic.
Returning to the topic, I think it's an important distinction that there's a big fundamental difference between "waving a bowie around" or otherwise flaunting your knife in public, and just showing a coworker your knife.
We should NEVER have to be afraid to show our knives to other coworkers who are interested, just because some other nosy coworker might wander by. It's impossible to predict that, and really, it's NOT their business to come over when you're sharing a LEGAL interest with another coworker, and make it their business. How are we supposed to educate people?
Regarding the explosives argument--steel doesn't have the same kind of issues with chemical decomposition and becoming unstable that explosives do. While I could post up the details proving this point, I think a bit of self-examination should quickly defeat this argument for most people. Honestly, if you think knives and explosives are even REMOTELY in the same category, I challenge you to keep some heavy explosives around you and treat it with the same care you treat your folding knives. Do this for 20+ years (assuming you survive that long).
The other point I found really interesting was the debate about "people kill people, not <insert object here>." Think about it this way: how many stories have you EVER heard about a knife just jumping up and stabbing a person who was walking by? But there are the rare but occasional stories about a gun misfiring and killing an owner (yes, you shouldn't keep a gun loaded, but even ammo can misfire without being in a gun, unlikely as that may be). For instance:
http://timesofindia.indiatimes.com/...-three-children-in-HP/articleshow/5666129.cms
http://www.deseretnews.com/article/469805/AMMO-NOT-LAND-MINE-KILLED-US-SOLDIER.html
A knife isn't going to just randomly kill someone. All kinds of reasons, from the fact that we've probably all survived an accidental knife cut, but it's considerably more damaging if you have an accident with a gun.
The other main difference between knives and other objects is that knives have a WIDE variety of important and useful purposes. That's why they're one of the very oldest TOOLS known, from the rock knives made by our caveman ancestors, to the streamlined machined offerings from our favorite knife companies today. They can be USED as a weapon. So can a stick. Or a brick. Either of those are FAR more lethal in a combat situation than a 3" folder. A gun, in contrast, you aren't going to use to open boxes, or dice carrots in the kitchen, or fillet a fish (puree maybe, but nothing involving precision).
So the point is, it takes INTENT or extremely bad luck, or severe carelessness, to kill someone with a knife. Even if you are severely careless, likely the worst that will happen will be that you'll get a nasty cut. I've gotten cuts from opening DOORS before. The same is not true of, say, an assault rifle. Or a mortar shell. Or something that is properly classified as a weapon, because it has only ONE purpose.
Consider:
http://en.wikipedia.org/wiki/Weapon
Intent is essential. That's why knives do not kill people. They do not have the intent to kill, nor is a folding knife manufactured with killing in mind. Some knives are, but most are not, and even those that are balanced as fighters are still very good at other tasks, and are more commonly used for tasks other than killing. I challenge you to find someone whose knife is used solely for killing. As knife aficionados, we are responsible for helping people understand the difference.