I say if one cop let's another off, then bully for them both. Most jobs have perks. It's no different than if your riding buddy who works at a bike shop gives you parts at cost while charging the guy behind you full retail, however nice that guy may be. I don't see cop-riders abusing this privelege because as someone said, the arresting officer may be more pissed and hold you to a higher standard if you ARE a brother officer. In fact, a friend who's a retired biker cop related a story to me (oddly enough the day I came home from jail for evading on my bike) about a fellow officer leading them on a high speed chase while off-duty. The runner eventually crashed and when the pursuing officers caught up to him, they beat his a$$ because he WAS a cop and he obviously wouldn't file police brutality charges against them.
My normal ride traverses several counties and I know there can be rivalry between jurisdictions which makes it better to be a citizen than a "rival" officer, depending on the arresting officer. It's unfortunate that cops are the sworn enemy of most of us when we ride hard, because one-on-one I think most cops are cool. They're underpaid for an extremely risky and essentially thankless job. Of course, the lure of power attracts its share of pricks as well, but they're everywhere regardless of profession.
My $.02
