Zzed's hack is excellent. Another one I would suggest would be "Trap Banned Memembers - They can't logout" by Logician. It puts a cookie on the users computer and they won't be able to log out or visit your site again until they clear their cookies. Seems to work pretty nicely on most users as they never seem to think to clear their cookies.
Or if he really starts annoying you, I could give you instructions for my "Idiot Ban" hack. It redirects the user to a website that will start opening somewhere between 20-50 little windows that scroll across the screen and starts singing "You are an idiot, hah ha hah ha".