Here's my one knife/cop story. I live in San Diego.
One day, several years ago, I go to Home Depot and park my motorcycle right up in front of the building. There is an empty police car parked in front of the building right next to where I parked. I was carrying a fixed-blade (Entrek Cobra) in a back pocket sheath, only the handle was visible. I unzipped my jacket before I went inside the store.
When I came back out to leave there were two cops sitting in the car. I stowed my purchase in my saddlebags, zipped up my jacket, put on my gloves and helmet, got on my bike, started the engine, backed out of the area I was in and was preparing to ride off when both cops got out of the car. They were two young looking cops (young to me anyways), with one looking like a kid (rookie I imagine). The older of the two said something like "Excuse me sir, would you turn off your bike". I turned off my engine and the cop told me that when I was at my bike, before I zipped up my jacket, that part of the jacket had covered my knife, and that technically that could be considered "conceald", (it's illegal to conceal a fixed-blade here). But this was just a friendly warning, the cop was totally cool, no attitude at all, it actually sounded like he wanted to help me avoid any possible trouble in the future. He didn't even ask to see my ID. He made no attempt to take the knife, nor did he ask for it. He just gave me the warning, I thanked him, and I was on my way.
And I've continued to carry a fixed-blade every day since then.
Several other cops have seen me carrying a fixed-blade, and yet despite being a bit rough looking, with my ragged black leather motorcycle jacket, and unshaven appearance, and riding a motorcycle, none of them have said a word about it. Some just smile at me in a friendly way and nod in passing.