All but four of my interactions with cops have been relatively positive. One of the bad ones was totally my fault, for which I escaped any consequences because the guy was a total A-hole and bitch-slapped the wrong person and, having been fired, was not there to present the case against me. Another was just cops doing their job running a speed trap; I wasn't pissed at the street cops, just at management for putting three cops running a speed trap just a month after telling me my stolen motorcycle wouldn't be investigated because "there are too many stolen." And only one was a real, true asshole.
I don't know I have any particular stories of positive interactions, just traffic stops where with the one exception (which again, I deserved) the cops have been uniformly polite (as have I - politeness and respect gets returned, as does showing your ass.) The only times I have needed them have been where I had something stolen, and although nothing was ever recovered except where we first located it, they have always been polite as they filled out the forms destined to disappear into the black hole of file cabinetry. (Except for the cop who "investigated" my stolen motorcycle, who spit tobacco juice all over my parking lot and solemnly told me it was "probably the ni@@ers. Yeah, the brothers are all about dirt bikes.)