If you do not have firsthand experience to the story being told, then the speaker has complete control of the facts he/she whishes to give you. Therefore, it does not have to be true, since the audience would be oblivious if the story was a lie. So, no, it does not matter if the speaker tells the truth or not, because the opinions and facts that the audience recieves is completely determined by the speaker, but only if the audience has no knowledge of any key aspects of the story.