How did his post make him appear close minded or whiny at all? Maybe judgmental, and he may have jumped to conclusions ( he's probably right though) about you being a rich little bitch.
If you want to have a successful sale, you 1. Probably don't want to piss off your cliental and 2. Should work on being a man of your word, like deleting your account and getting the fuck off newschoolers, like you said you would...
If you can accomplish these relatively simple tasks, I am confident to say that you will have no more problems with people hating on you, on this site anyhow.