The existence of sub-factions does not disprove the existence of a shared, overarching ideology. Those Christians who fought each other, how many of them didn’t believe in core stories like genesis, the crucifixion, or the resurrection? If anything, the fact that even people with shared ideologies will fight to the death over smaller differences should tell you how dangerous a multicultural world will become. I can tell you what a Christian, Muslim, and Jew generally believes. Your denial that these religious identities have meaning and define culture will not serve you well.