holy war

noun3

1. •
   A war which is primarily caused or justified by differences in religion and beliefs.

   • The conflict is beginning to look like a holy war between Sunnis and Shias.
2. •
   (Internet) 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. •
   The rivalry between the sports teams of Brigham Young University and the University of Utah.