The Believers can be viewed as an exposition of believers of anything. The primary object of the movie is the religion Santeria and the practitioners of that religion but, the underlying thread is that any fanatical and misguided believers in any religion are the same.
The black magic brand of Santeria practitioners weren't the only Santerians in the movie. There were others who were far less dangerous, even if their customs and ceremonies were strange. The understanding though is that in every religion there are probably messages or passages that are misunderstood by the fanatics and they end up doing extreme actions in the name of said religion.
The Believers goes deep into the black magic aspect of Santeria. By pure happenstance Cal Jamison (Martin Sheen) and his family get wrapped into that world. The movie is eerie and suspenseful as we are navigated through this strange religious world.
