The owner, licensee or operator of a visual or sound radio broadcasting station or network of stations and the agents or employees of any such owner, licensee or operator shall not be liable for any damages for any defamatory statement published or uttered in or as a part of a visual or sound radio broadcast by a candidate for political office in those instances where, under the acts of Congress or the rules and regulations of the Federal Communications Commission, the broadcasting station or network of stations, is prohibited from censoring the material broadcast by such candidate, provided the owner, licensee, or operator shall cause to be made at the conclusion of the broadcast the following announcement in substance; "The broadcast you have just heard was not censored in accord with the immunity from censorship extended legally qualified political candidates."