Try punching a nice big hole in the aft 1/4 of their car next time...it might make them come to their senses!
Seriously though, this sort of thing is a bit of a problem, especially with the plethora of fast, pointy RTR's out there operated by, shall we say, the less experienced. I don't have an answer, except that 'Little Johnny' will become bored soon enough (after a couple of weeks probably) and vanish never to trouble us again. There will of course be more, but I don't suppose we can do much about that either!
Mind you, back around Christmas time, I was on my local lake, along with several new Christmas Presents, most of which had conked out within 3 foot of the bank. In the spirit of helpfulness, I guided my MTB towards one to push it in to the side, gave it a gentle nudge and promptly capsized it, so I guess none of us are perfect, are we!
Hope the repairs go well.
All the Best
Mike
(Why Flag D? It means, when flown alone, "Keep clear, manouevering with difficulty"...and I'm still flying it 6 months later!)