How do I get Yahoo's attention regarding a troll?

I frequent the aircraft section and over the last several months we have been having some trouble with a troll. We have all seen them, usually they come in, ask a few dumb questions, give a few bad answers and like a bad rash are gone in a week.

If a troll is a rash, this kid is herpes. He just doesn't quit. As far as I am aware, he has 5 different accounts. He misrepresents himself and gives answers that are quite frankly dangerous. We have many student pilots asking questions, and if one listens to something this kid says someone could end up dead. He has altered his account to impersonate others, which is disrespectful at best. He also enjoys making absolutely inconsiderate and inappropriate comments. While those get removed quickly they still happen.

I have reported every single thing he does that is in violations of the guidelines, and I know others have as well. It is my best guess that some of his accounts have been shut down, but if he just makes another account then we're right back to where we started.

I have contacted several of the other people who often answer questions, and we have agreed to ignore every thing he asks, but there are simply too many people giving answers to get everyone on the same page.

While I'm open to any ideas to get him to stop (one person sent a very heart felt reply to him about an answer he gave about 9/11 that would make anyone with a heart at least a little teary eyed, but to no avail) I want to know how to contact someone at Yahoo and get his IP address blocked.