Hide the Decline and STFU

In his letter Mann threatened legal action, claiming the spoof video "illegally used his image and defamed him."

Neither Mann nor Penn State responded to requests for comments. Mann's lawyer, Peter J. Fontaine of the Washington D.C. law firm of Cozen O'Connor, told FoxNews.com "we don't comment on any pending legal matters for clients."

Davis and No Cap and Trade said they welcome the lawsuit.

The group is eager to conduct an in-depth probe of Mann's work and "finally look at how it was done. We understand why Michael Mann is eager to silence public discussion of the hockey stick scandal, but truth is an absolute defense."

Sometimes silence is the best strategy. But last time I checked, there was no legal cause of action for being offended. Yes, I know defamation is, but Prof. Mann's allowed himself to become a public figure, so he would have a tough row to hoe, not to mention a lack of damages. Last time I checked, he's still got his tenure and paycheck.