Hell, I'd take it a step further. Don't even tell them they're being banned. Apologize profusely while they're abusing you. Get their address and promise to send them something extra to make it right and keep their business.
Imagine their anticipation when they get their package from Tasty Vapor and open it up, expecting some heavenly juice and some extras because of the "issue" that they "resolved" by berating you. Now imagine their surprise when they actually open it up to find...
...a picture of Geoff giving the camera the finger. And a frozen dog turd.