The short answer:
1 - many people have a pervasive belief that they are weak, victimized and oppressed, which is usually brought about by poor parenting
2 - their response is to attack or otherwise seek revenge on those who they perceive as their superiors, their oppressors or any person or institution they believe is "winning" at life. They believe that something "unfair" must have resulted in them being weak and victimized, while someone else is strong and "winning".
3 - to them, a knife is objective evidence that the other person is in some respects "superior", because the knife allows the knife owner to impose his will on the weak. And as they believe it is "unfair" for someone else to be superior, they feel morally justified in creating workplace environments, social morays and statutes of law which prevent other persons from carrying knives. After all, its only "fair" that the oppressor be made weak and oppressed.
Notice that I said "belief" and "perceive" and "feel", because this worldview is purely subjective and emotional. Those who feel weak and victimized are not in actually objectively weak and victimized, and those who they believe are "superior" or "stronger" or "better" are not actually so. Its all about perception and emotion.
My thinking runs along tracks that are more or less parallel to these. Some differences in phrasing and reasoning, but pretty close. What I describe below may sound like it's substantially different, but it is of much the same theme and spirit. It's mostly the result of observable behavior, and a descriptive framework to help express what I understand about that.
There is (for lack of a better word) a pathology about certain people that inclines them to attempt to negate or neutralize anyone perceived as being strong, able, effective, or creative. I will refer to such people as proto-antisocial (not a clinical term). These are -- at least the hard core ones -- a very small segment of the population, maybe one and a half or two percent. That little spot way over on one end of the "control-freak" bell curve. Threatened by independent thinking and creativity, they seek control of others through means of nullification.
Perhaps twenty percent of the population is "in sway of" this proto-antisocial crowd, and the resulting apparency is that there are more rabid "hero haters" than there actually are. Nonetheless, this twenty percent is very hard to reason with, given that they have a kind of pain avoidance response to the proto-antisocials which tends to make it hard to have a rational conversation on certain topics. Think of these people as the unwitting minions of the antisocials.
A knife is a tool. The implication of carrying such a tool is that a person is
a) not intimidated by sharp things (strength),
b) in control of his environment (able, effective), and
c) capable of independent action and thought (creative). Seen in this way, a knife is a "symbol" of power and control, whose owner may actually be capable of making things happen and controlling events.
Independence and power and self-determinism are intolerable to the proto-antisocial, who only feels safe when things are stopped and people rendered incapable and ineffective. They will prevail upon the minions to make things uncomfortable or miserable for anyone not conforming to some acceptably introverted profile. This is done using whatever tools are available: legislation, regulation, PR campaigns & propaganda, education, and indoctrination.
The good news is that, while the proto-antisocial and his minions may swing a lot of weight, they are not the majority.
The other eighty percent of people are reasonable, rational, productive people, and a well-reasoned conversation will often be all it takes to fix the false impressions from propaganda and establish that a willingness to control one's environment and to be properly equipped and prepared is not an indicator of insanity or criminal intent, but rather the sign of a healthy mind and outlook.
How did the antisocial control freaks get that way? That's beyond the scope of this discussion. You need only be aware that they're out there, and that a not-insignificant portion of the population tends to mimic that viewpoint.
The fact that there really aren't that many (as a proportion) of these folk is not to say that they can't be a real hazard to your well being. Some several of these will actively work to position themselves in places of authority, and that can result in hostile work environments, in spite of the fact that all your peers are just fine with tools and the self determinism they imply.
I've had the opportunity to engage at the "minion" level, and discovered that "ordinariness" works well to draw the sting from the usual attack vectors. I carry more than one knife. That is seen as "unusual" by some. Well, in addition to the usual "right tool for the job" argument and the "spare tire & fire extinguisher" idiom, I also carry multiple pens, multiple flashlights, multiple Fresnel magnifiers, multiple gas cards and Visa cards. So in the end, when the "but why do you carry more than one knife" question lands, at the very least I have the "why not, I carry two of everything else" response.
I'm generally seen as the "gadget guy" and that earns me requests to borrow this or that, or "can you open this" requests.
It's quirky, but it's not threatening.
As some of the other guys have already mentioned, at least one of my EDC items is a "cute" or "refined" pocket knife -- usually a slipjoint -- that is almost universally acceptable. If I pull out my green-handled John Deere medium stockman or my Paul Presto and someone wisecracks about a "weapon" I have a quiver of ready responses, which I've almost never had to use. Calling a cute or refined pocket knife "dangerous" or a "weapon" will at the very least get my Spock Eyebrow and a "really?" or some vastly exaggerated brag about the gang of bikers I cut up with my awesome two-inch blade. "Yeah, man, they was shakin' in they boots when I whipped out my plus-five pocket knife of pain and terror."
It's a mistake to hide from interaction, just as much as it's a mistake to flaunt "tactical" hardware around squishy thinkers.
We've lost a lot of ground in this country, and we've slid from a "culture of competence" from my boyhood -- when we
all carried a knife at school -- into a kind of "culture of cowardice" where it's chic to be frightened of tools.
That's ground we need to win back. It's a gradual thing, but it is actually winnable.
Send signals that are easy to receive: have a "civilian friendly" gent's knife on hand for everyday social environments. Be willing to receive and handle the signals that are sent back to you: gently explain how ordinary and sensible it all is.
We win when knives in pockets and on belts are once again completely unremarkable.
" Most people know I carry a gun, if they don't like it... tough. I am a responsible individual. Better to set a good example then to conform to BS. 
