Good post, thanks Hasek.
Personally, I'm not much for collusion... If we observe and allow dangerous activity to continue, we take on a portion of the responsibility, imho.
Granted, there is some tact required, hard finger-pointing will rarely yield a good response.
Typically, I break some common ground, try their kite, let them try mine, then cite a scenario "similar" to theirs, without out and out naming them.
You know, build up, try and give them some context with which to realize their own role... If no dice, escalate in stages, most folks really don't intend be be jackasses, they're just missing enough pieces that they continue to overlook the big picture... "It only takes one crash, just one pissed off person, the 'right' one, then we're in front of a city council defending against a kite ban at our local park, ya know?"
Granted, that's just my style, but it works for me... I really hate to alienate folks from kiting (local or beyond), just about as much as I hate to see poor kiting etiquette.