This buyer was just interested in wasting my time.
Made an offer and we negotiated. After I would accept the offer, he would try to negotiate and go lower again. I would accept and he would do the same thing again.
Eventually I refused to sell it to him - which is why he is annoyed.
Any seller has the right to refuse to sell an item for THAT cheap. It is my right to decline your offer.
Thanks for the feedback anyway.