I ride motorcycles. I have a Ju-Ju bell on it. The superstition is that the sound keeps the gremlins away. Do I believe it works? Maybe it does. I have no way of knowing what would have happened in the course of my riding if I had not had the bell on the bike. By your statement I'm an idiot (or at least a borderline idiot) and stupid.
If you rely on the bell to keep your motorcycle running, and disregard preventative maintenence, I may very well call you stupid when the engine siezes.
If you rely on the bell to keep you safe and in your superstitious confidence leave your helmet at home, weave in and out of traffic and pop wheelies at 100MPH, I would also call you stupid.
On the other hand, it sounds as if teh juju bell is there more because you like it, and not because you believe it has magic powers.
Many people have good luck charms. Myself included. I keep mine more for what they mean to me (a gift from my father before he died, for example), than the belief my "luck" is better. To me there is a huge difference between having a strong feeling about an object, and believing that it has super powers and makes you special because you own it.
Some superstitions are fine, like baseball players. Their's may have some basis in reality. By that I mean the key to success in pitching or hitting is to do the same thing every time. Part of that may be to wear the same socks, or shave at the same time. It all goes towards consistency. I'm not saying those are magic socks, but the act of being consistent in the locker room may translate into being consistent on the mound.
Luck=chance taken personally. I don't know who first said that, but I heard it from Phil Plait.
I have heard the banana myth may have gotten it's origins in reality. Spiders and snakes live in banana trees, and may have been brought on board and caused problems with bites to the crew. So back then, thinking bananas caused problems wasn't irrational. However today, it is, as surely unless you are allergic, bananas are harmless, and even if you are allergic, they are certainly devoid of magical powers, for good or evil.
I think most people can agree that bananas are not magical. Therefor why should we respect the belief of someone who thinks they are? More importantly, why should we place our trust in this individual?