Witchever (intended) particular belief system you adhere to, including none at all, 'do as you would be done by' is not so much a rule as a fact.
It's not universal by any means, but if you spend your life slinging misery and unhappiness around, it will tend to reflect back on you.
Just another ultimate truth.
As for the 15 year old reprobate - I'm guessing all this behaviour is making him feel like a big man.
Speaking personally as someone whose moral compass was depolarized long ago, I'd capture his face on film or digicam, and then photoshop him into some scene that will make him out to be a big girl's blouse. Do some detective work, and then post these images everywhere he hangs out.
Alternatively you could kill him with kindness. (drop a big bag of pound coins on him from a great height).
This sort of utterly unexpected tactic can work by totally wrongfooting people. Turn up on his doorstep with a cake and say its for him because he's such a generous and helpful soul who really adds to the community. Get others to do the same, leave him flowers, cuddly teddy bears etc.
Like rough music only quieter. And hopefully wont lead to a cycle of vendettas...
for those that are interested - Rough Music Description
Justice the way it used to be...not saying that things are better or worse now, just different
Or finally there are the riskier, less morally acceptable solutions:
1. Pay a bunch of lager swilling maniacs to beat the living snot out of him.
2. Carefully goad him into breaking the law so that you can capture the moment when he sets fire to your car or something
just my £00.025...