I have been sprayed with stones here in NZ too. I suppose I might be inclined to do the same. Little blowfly buzzing around my butt.
Its like someone standing too close to you. Its about standardised distances. If you go to another country or sometimes even another town everyone drives different.
On my scooter I nip in and out, travel past cars on the inside etc etc and people totally freak out!
In asian cities I would be called Mr Careful. Here I'm Mr Dangerous.
Usually 30 years plus males in large cars are the most offended.