With the internet there is an aspect of anonymity. It is similar to the the driver that cuts you off then gives you a dirty look and a hand gesture, the finger. The same person would not do that in line at a grocery store.
Years ago before the internet there was a paper called the Want Ad Press.
Buyers would contact sellers on the phone and make an appointment at sellers home. There are also buyers that are not happy unless they haggle the price down even if it is very reasonable to begin with.
A buyer came with his son to by a hard to find item which his son really wanted.
Dad tried to talk me way down for a half hour on an already great deal.
It became insulting. I finally said that it was no longer for sale. He then agreed to my original asking price, where I explained that I had decided to keep it. (I just didn't want to sell to him at that point) He then began arguing that I HAD to sell it since It had been advertised.
I politely asked him to leave, which he refused. I gave an option of physically throwing him out or having the Police escort him out. He called back after he got home to again offer to buy at my original asking price.
I think he wanted to teach his Son how to haggle. That lesson backfired.