The other driver was not trying to promote a citizens arrest or give you the bird, he was calling to your attention the fact that you were littering, breaking the law, and screwing up mother earth for the rest of us.
I haven't bought a new car lately, but I absolutely don't believe that they don't have ashtrays in cars anymore. It's more likely that yours was full, and you were too lazy to take it in the house and empty it. I bet on those rare occasions when you do empty it, it's always on the side of the road waiting at a stop light or going down a more private secondary road when you stop at a stop sign and no one's around.
If you don't have an ashtray in your car, buy a cheap one from the store and leave it in your car. They also make disposable ashtrays nowadays that are small enough to fit in your pocket or pocketbook. There is absolutely no excuse to litter. Littering one of the major reasons that give smokers a bad name.
By the way, I was a chain smoker for 25 years, and never once did I throw a cigarette out the window or litter the ground.
More information about formatting options