Thanks for the input, Tanya.
So much of your post rings true, but I have to disagree about most cops being terrible judges. By and large I think they're pretty reasonable people and able to size up a situation well. The problem comes when you draw a large group of them, because one or two are bound to be hard-asses and can affect the entire group. When I launch into my idiot-grinned rhapsody about the light, color, contrast of what I was shooting I pay particular attention to make good eye contact with both the nicest and meanest cop in the bunch -- completely win over the one and make headway with the other and it seems you're in the clear.
As far as rights go, I don't think any of these guys want to be lectured or badgered. but it's all in the phrasing. I always say, "Jeeze, I thought it was legal to photograph from a public street, was I trespassing?" Then they have to admit I wasn't trespassing and gets them in the direction of conceding which laws I hadn't broken and that I had, in fact, broken none.
This was my sixth major run-in with cops and they've all turned out okay eventually. I was just wondering whether there was a way of getting past the initial "I could die if I make the wrong move" stage more quickly. I've decided to print up some "Michael Veit -- Photographer" cards so I can pass one along with my license first thing. Seems like it couldn't hurt.