Well everyone understands "Bible" too, but we don't call the holy writings that.
Yeah, and?
"Crusade", in English, is much less Christianity-connotated than "Bible" is.
I don't know whether you're a native English speaker or not, but if you are, then you're being unnecessarily—and somewhat annoyingly—pedantic about this.
Please, don't try and rewrite half the English language just to excise the influence of Christianity from it. It's way, way more trouble than it's worth, and will confuse people if you start using your new words like they're supposed to know what they mean.
