First and foremost, you were not threatened.  You were notified that your actions, if continued, will lead to litigation.  That is not a threat, that is a legal remedy to libel.  We are filing for an injunction of your site today.  I guess we will see if it was a threat.  We will also be launching an Operation against Wikipedia for being libel-mongers and will test the capabilities of your staff, system, and personal lives.  That, my friend, is a promise!