Liability shall be denied and no recovery shall be allowed against the owners, licensees and operators of any visual or sound radio and television station or network of stations or against the agents, servants or employees of such owner, licensee or operator, for the publication, utterance or broadcasting of any defamatory matter, where the publication, utterance or broadcasting thereof is not subject to their censorship or control by reason of any Federal statute or any regulation, ruling or order of the Federal Communications Commission.