Meh, no biggie... there's no way he could possibly have so much free time to ruin every
mock draft up there, or even half. So, if you aren't happy with one you're in, dump it and try another one.
Honestly, with as strange as some of the Yahoo! rankings are, and as bad as half of those people are, it probably won't make that much of a difference. If you're in a casual league, just pretend like he's the crack-head drafter who has some messed up strategy and learn how to work around him.
Unless you're in a competitive big-money league, there's a pretty decent chance you'll end up with people drafting almost as bad as this guy. And if you are trying to prep for a competitive league, generic Yahoo! mocks with nobodies probably isn't going to prep you very well anyway.
Take it for what it is... nada. Close it, open up another one, try a different site, or just deal with it. Complaining about it is exactly what he gets off on, for whatever f'd up reason.