While I can offer no valid advice or experience on this "warning" thing, I know how you feel and I definitely agree with you. I'd be pissed, too. It's not so much the consequences of the warning itself in regards to your license, insurance, etc., but in a way your good name has been sullied by an obviously false accusation, as noted by the response you got from your inquiry with the state police.
Laws are laws. Not only do we have to follow them, but I believe any law enforcement officer should, also. I have nothing against cops in general, but I really don't like that "what you may think is prudent or safe a trooper or police officer may not believe it" clause that seems to be used a lot.
It's either against the law or it ain't. In your case, what you did obviously wasn't. I don't think any law enforcement officer should issue any kind of violation or warning unless a law was observed being broken, not based on their own "judgement."
To me, that's the same thing as me claiming that my "judgement" led me to believe it was safer and prudent to drive/ride faster than a posted 55mph speed limit and therefore it was okay to do so.
It's either against the law or it ain't. Allowing law enforcement officers to basically create their own "laws" on the spot sets a precedent that I don't really care for.
One could argue that in real life a lot of situations come up where somebody is obviously being stupid or dangerous while not breaking a law. Certainly not to say that what you did, Some Mook, falls into that category. It definitely doesn't.
My opinion? Any kind of "warning" or violation that revolves around an officer's "judgement" instead of an obvious breaking of a law should entitle the recipient of the ticket/warning to a free, face-to-face meeting/hearing/whatever with a judge and the officer who issued the citation so both parties can present their side of the story. The officer should provide clear, concise details about the occurrence in question, not just state that he "thought" what you were doing was a bad idea.
I agree with Stinker. Send a copy of the citation and a letter explaining your side of the story to the state police and see what happens. Might be nothing, but at least that shouldn't cost you anything. If there are other avenues to fight it, I guess you'd have to decide whether or not you wanted to spend money to do so. Tough spot you're in, man.
I'm a law-abiding citizen and I respect law enforcement officials, but they should make their decisions using existing laws, not their "judgement," "experience" or any other blanket term for personally deciding that while what you're doing isn't against the law, it's not "safe," or "a good idea," or "prudent."