It is inconsiderate. He should've come and warned you he was about to make a mess and given you the chance to move the car.
Is it possible he genuinly didn't realise? Going by your comments, it seems he's a general all-round twat, so probably just didn't care.
When we have a bbq at home and notice the neighbours have washing out, we go and tell them we're about to light a bbq so they can get the washing in. At least we used to....until one day one side lit a bbq without telling us and smoking out our washing.
My rule is simple....treat other people how you would want to be treated....UNTIL they feck you over....then its all out war!