Unfortunately, while there may be, technically, a way to get him to stop -- you may be able to bring a defamation suit against him if he is making factually false claims that are harming someone -- it's almost always a bad idea to do so. Few such claims succeed; it is expensive to bring them; and the publicity resulting from filing the lawsuit always ends up bringing more attention to the blog posts you don't want people to see than they ever would have gotten otherwise.
This is not legal advice, just practical advice: This person is clearly thriving, as you say, from the attention he is getting with his little project. And as an adult you know exactly what is the best way to battle such childish behavior: Deprive it of oxygen by leaving it alone. Stop clicking, stop commenting, and just see how fast (even if there's a brief and unpleasant up-tick of desperation) he stops blogging.
To add to Mr. Coleman's post which is unfortunately a painful reality for many online scenarios such as this, defamation claims rarely succeed because the posters are generally clearly spewing invective "opinions" not "facts." If it is clear that the comments are the poster's opinion, generally speaking in most states that will not suffice for defamation. Although, sometimes it might pay to send an attorney demand letter (assuming this is not a complete attention seeking "yahoo" who might actually post the letter and further ridicule you) to see if the posts stop. However, that is a sensitive judgment call driven very much by the psychology of the poster rather than the law.
I hope this helps.
Disclaimer: This answer is for informational purposes only and does not constitute general or specific legal advice, nor create an attorney client relationship.
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