Google's Adsense may make cents, but it doesn't always make common sense.
Look at this screenshot grabbed from a web page I reached through an unsolicited email. Specifically, check out the sweet Google ad in the bottom right hand corner (click for the full-size image):
Somehow, I doubt the site owners would be pleased to have that ad on their webspace.
Then again, it's gotta be at least kinda cool to have people pay for the privilege of insulting you. And if nothing else, the ad revenue might work as a small down-payment for the libel suit.
If a long-time regular, you may remember this previous post on Google Ad irrelevance.