Well obviously, because a significant part of the world population remembers either directly or culturally what happened in the name of christianity and/or islam.

Here in germany for example we still have monuments and official holidays/festivities directly made after the 30-year-war 1648. We also still have towers standing where "witches" used to be imprisoned. And so much more.

This kind of living history is a thing in many parts of the world. Just because christianity got comparably tame in the last 100 years or so, doesn't mean that it doesn't count. The relative impotency of the christian churches in europe was paid for with blood. Lots and lots of blood.

Americans lack this kind of living history, because they don't really have any. But elsewhere this is quite normal to be in the cultural consciousness.