Lowballers

We had my son's Honda CRX for sale asking $800. I had a guy call me and offer 650 but I was on my way out of town and wouldn't be back till Sun/Mon. Another guy called me and tried to offer me 400. I told him I had another better offer and he was not even close. He then tried to offer 450. I said, I had someone coming to look at it on Monday, call me after that to see if it is still available. I do not feel I have to tell him my current offer as it is none of his business. He then states, "So I can have it for 400 after Monday?" I said no, that another guy was in front of him and if he was serious about buying it, he would have to call after Monday and make me a better offer. I then made a "note to self" in my mind that I am not going to sell to this asshole, even if the other guy passes... Who is this guy to think he can come in after another guy gets in line and try to buy it cheaper???