I worked customer service for years when I was going to school and some of the worst customers I ever got had to be when I worked at the return desk in Walmart.
I had one older lady bring a potted plant up to the desk from the floor asking for a discount because it 'didn't look like it had been watered today and it was the last on the shelf' (the plant looked fine not wilted or yellow just a little dry). I told her I could give her 10% and she got really angry and went on a rant about how she should get it for free because she spends so much money here and we are probably going to just let the plant die anyway. I appologized and said I could get the manager if she didn't mind waiting 2 min. She then called me a stupid bitch, threw the plant at me and left.
I also had guy that bought 4 bikes from me then 20 min later came back wanting to exchange them for new ones because he hadn't hooked them up to his RV properly and they fell off when he backed up and he ran over them. The worst part is that the manager actually replaced the bikes because the guy was such a dick about it and argued for over an hour.
Not sure a website would really stop people from being assholes, the company holds the employees accountable but individual people wouldn't care especially if they act like that in the first place