Maybe you haven't read the site documentation, but Anonymous Monk is not *one* user. It's any user who has decided to post anonymously for whatever reason. You can see a healthy discussion of it here: Anonymous Monk?

Though I understand your paranoia at this point, I really doubt it's just *one* person who's messing with you. Really, I'd suspect a LOT of people messing with you at this point because, well, you react to it. If you really don't want to antagonize people, you could just stop responding, which countless people have suggested already.
Why do you keep coming back for the abuse? Is even the negative attention validating in some way at this point?