My client found his name as a sponsored link which lands on a slanderous article. I called Yahoo, they compared this to all the people bidding on britney spears, and stated that it's not against their TOS. Their suggestion was to pursue arbitration. I researched the offending site, arbitration isn't going to happen with this guy.
You are likely to have better luck going after the site holder directly. What you are talking about is not a violation of their TOS. So unless you can get the guy to actually stop publishing the material, there is probably not much you will be able to do.