holy war

Short definition from Wiktionary

Noun

1. 1
   A war which is primarily caused or justified by differences in religion and beliefs.
2. 2
   A long-running and acrimonious debate or flame war over personal preferences in technical matters, such as the choice between little-endian and big-endian representation.
3. 3
   The rivalry between the sports teams of Brigham Young University and the University of Utah.