You shouldn't comment on how messy someone's car is.
Joe is getting a ride from his friend, who's car is messy.
Joe wants to ride in a clean car.
Joe offers to help his friend clean his car quickly before they leave.
Joe calls his friend a pig and demands he clean his car before he will get in.
Joe's friend gratefully accepts, and they head out in a clean car.
Joe's friend leaves and refuses to give him a ride.