Very few are credible. Just because a person believes something stupid, that does not make it credible though. What most people fail to understand in life is that most of the time it is better to keep their mouth shut.
Everyone has the right to disbelieve other people's predictions and also has the right to believe them for a reason. But I don't know what you call stupid, because basically everyone has the choice to believe or not what others say. Furthermore, everyone is strongly encouraged to believe in themselves, as long as they possess abilities far above average. Therefore, it's natural to distrust the words of others, including their experiences. However, for those who are learning to understand something they don't yet understand, they will probably continue to search for it from various sources, even if not everything they seek is immediately credible.