Zealotry is when someone takes a religious, cultural, or political belief too far, refusing to tolerate other perspectives or conflicting beliefs. People say that zealotry springs not out of faith but doubt. Makes sense.
Zealotry is believing so strongly in something that you are completely intolerant of different beliefs or opinions. A government's zealotry might lead it to outlaw free speech and arrest journalists. Zealotry comes from the noun zealot, or "fanatic," which is rooted in the Greek zelotes, "a zealous follower," ultimately from the Greek zelos, "zeal, ardor, or jealousy."