Not to be a jerk about it, but you need to throttle it down a bit and grow a thicker skin. Getting angry over trivia is the ticket to a heart attack sometime later in life. Take a deep breath, KNOW that you will be deleting messages and do just that ... delete it. Try to smile while you do it; you'll feel better.
As for the price, I say list it for what you want to sell it for, and don't sweat it if someone disagrees, especially if that someone is not waving a check in front of you for some reasonable (as in an amount you would accept) offer.
When I sell something via Kijiji (Craigslist is available in Canada but nobody here except hookers and puppy mills use it) I expect lowball offers, and maybe even insulting or troll messages.
Just about every eMail application has some mechanism whereby you can create "rules" or scripts to deal with messages. I have one that deletes the message instantly, not even stopping to spend a week in the trash. I do not reply to the message, and I add the sender's eMail address to my rule, so that I am never bothered by this person again, not just now, but for all time. After the first message, I never even see another from that address. Works very well.