Yea, the only fair thing to do if he "doesn't care" would be to delete him, he already got all his levels from botting, so it's not exactly fair to the rest of the server if you just allow this to continue when you are already aware of what he has been doing... All that will happen if you ban him is that he will do something else for a few days then come back and bot some more.
People will stop donating if there aren't any rule enforcers here because it's no fun to play against super botted chars because even if you kill them they take 10 more levels at night when people are asleep. No donators = no dedicated server, unless you wanna pay for it yourself, in the case that you don't I would start banning/deleting persistent botters.
Ralphie.