FWIW, I thought the seller was being more of an ass. The buyer offered a low price, but it wasn't ridiculously lower than what a dealer would ask for a trade in. That's just part of negotiating.
Secondly, he asked nicely if he may have the VIN, probably to run a carfax report. I would think that's a completely reasonable offer if I'm purchasing a used luxury car.
Instead the OP makes a childish reply. A simple and courteous reply turning down the offer or making a counter offer would have suffice.