It is quite clearly his problem, the people claiming otherwise lack any logical thought. It has nothing to do with being a good neighbour. Your car remains secure while his is not. His car is obviously the one with the problem. I'm not saying **** HIM LET HIM BURN, I'm just pointing out that the problem lies with his car not yours.
"Not the sort of people I'd want as neighbours" Why don't you take his car to the VW/Skoda garage for him, now there's a good neighbour. If you wouldn't do that for a neighbour then you are scum, sub human scum.