I learned not to get angry at them. They don't know better. Plus, when I get p!ssed at them, while still holding the knife, now they really freak out, and look at me like I'm a psycho. So, I don't take my frustration out on them -- it closes the door for possibly educating them, and they dig in their ignorant heels even more. their reaction is emotional, not rational, so the explanation has to reframe how they FEEL about the knife, not what they think about the knife. First make them comfortable with you, then make them comfortable with your knife.
I think of it like the movie The Matrix. They don't even know they've been brainwashed and are living an illusion. I gently take them through the process, keeping them at ease, and describe the productive uses I've gotten from a knife. The "rescue" stories that i di with my CQT Magnum work very well. It explains why I have such a big blade on me. I explain that with a smaller weaker knife, I'd have been unable to help two people out who were in a jam.