Dear AJ,
I don't think you appreciate what people here are trying to say. No matter the severity of the issue, the question is your end game: what is it you hope to accomplish, and does this method have any chance of success?
Does anyone truly believe that this passive aggressive signing is going to cause these "kids" to stop doing this? I think it is blatantly obvious that having these crowds of "peaceful protesters" - well-meaning as they are, and the offenders behaving in a manner which is truly painful to witness - is more likely to backfire: The "kids" may move alright, but to a more central location so as to create a greater commotion (or it may create fist fights, as mentioned above).
You compare it to עריות (though I don't understand why) - so take the comparison further: if that was what was happening, would you send groups of men and children to sing songs near them? (What songs would you choose? Now there is a more fun discussion.)
Please stop building and destroying this straw man. It's getting tired and old fast.