Sorry, I had hoped to spare you this, but you now may be subject to a lawsuit.
It is not at all uncommon for attorneys representing a trademark or copyright holder to send a "cease-and-desist" letter to someone believed to be infringing. I think it is less common (or, as my copyright lawyer put it, "crazy") for attorneys to claim that the cease-and-desist letter itself is copyrighted material and that their rights will be infringed if you tell anybody about the letter. It seems that recipients of these letters who think the claim is bogus frequently post the letter on the Internet for purposes of mocking it. Apparently, the law firm that wrote this letter hopes that claiming the text of the letter is copyrighted will prevent this.
I don’t know about that.
It didn’t deter the public-interest group Public Citizen from posting the letter it got, saying that it was firmly convinced that doing so constituted "fair use." Public Citizen’s response letter (also posted on its website) concludes by saying that it invites the firm to sue Public Citizen in order to test its interpretation of the fair-use doctrine: "By this letter, we are inviting you to test the validity of your theory that the writer of a cease and desist letter can avoid public scrutiny by threatening to file a copyright law suit if his letter is disclosed publicly on the internet."
We shall see.