Why Is This Knight's Holy Light Red?

Lu Xifa traveled through the world of swords and magic and became a paladin with red holy light. The church regarded him as an oathbreaker and wanted to eradicate heretics; the nobles regarded him as a traitor and fought against him to death; people were afraid of punishment and everyone was in danger. He has been working at the grassroots level for eight years, and all he has is a red oath. So he established a knighthood, trained paladins, managed the territory, and built a team. In this world where extraordinary beings slaughter mortals wantonly, standing behind him are countless people with red holy light like him. "I will not keep this oath to myself!"