IMHO, I don't mind "Guest" posting, usually they contribute which is great. But since you guys can track IP address'. There should be a one strike and you are out policy in dealing with "guest".
Idiots like this do nothing to contribute and its my guess that he/she would never have anything plausable to contribute overall. He is obviouslly beyond help so the cafe has little to offer him, since we don't provide any mental health help.
I honestly do not see the harm in blocking a few IP address' ..