Before science, we used myths and legends in an attempt to explain the unexplainable.
Today, thanks to the hive mind of the internet and the scientific method we can observe and test. As a result, dismiss many of these false beliefs as superstition.
What predictions or promises has this organization or person made that have come to pass? With time, many things can be proven or debunked. One only needs to examine the history to see what was said and what has happened to find inconsistencies.