Man, this thread swirled right down the crapper.
Anyway, knives have been around for a long, long time. People pretty much have their minds made up how they feel about knives at this point. I've always seen a pocket knife as something that makes everyday life easier nothing more, nothing less. Others see a pocket knife as a weapon. Unless I am a master debater (LOL), I'm not going to be able to sway someone with my words.
Now, if you take the same person that sees a pocket knife as nothing more than a weapon and put that person into a situation where they need a knife to save their life or the life of a loved one then I think they will see the advantages of having one. Before you jump down my throat, I am not speaking of a self defense situation, I am speaking of something different. Maybe the old article of clothing stuck in the escalator scenario? Does it happen often? No, but has it happened? Yes. Even when someone hits the STOP button on one of those things it doesn't loosen the tension it already has on the clothing. A knife would be needed to cut someone free. I believe that the people who witness or are a part of something like that would feel very differently about pocket knives from that day on. Unfortunately, people don't easily change their beliefs or their minds and something life altering is often the cause for someone seeing something in a different light.
I live in NY, about 30 north of the Bronx, and I've never once run into any trouble for carrying a pocket knife, but it may be because I use good etiquette while carrying a pocket knife. The easiest thing to do is to never remove your knife from your pocket unless you need to. Don't stand up against a building flicking your knife open and closed. Don't be a dick and start trouble when you're carrying a pocket knife (actually, don't do this at all). If you like to drink hard at the bars then it's probably not a good idea to have your pocket knife on you. Sorry, but the drunker you are the more chance you're going to start acting a fool and pull out your pocket knife whether it's to show your friends or you are just so used to fondling your knife you don't even realize what you're doing. Don't bring your knife into places that you aren't supposed to have it, obviously. If you work at a place where you are going to be using your knife in front of customers you should carry a proper knife. You don't need a folding sword to open boxes. If you have to open a cardboard box for a customer don't wave open the Cold Steel Spartan you have in your back pocket. Pull out something appropriate and open it slowly and inconspicuously. There is no need to scare the customer. The absolute best advice I can give is that you act like you don't even have a knife in your pocket until you need it. You should be fine. If someone still has something to say when you use your knife in front of them then just smile, nod, put the knife back in your pocket, and walk away. Why waste your time on the dim witted?