not only is western civilization not built on top of christianity, but the christians did everything they possibly could to stunt the growth and development of western civilization.

if western civilization had never conquered the church, the europe of today would look a lot like the middle east does.

rather, the basis of western civilization is greek philosophy, and it's corollary of science. christianity and islam are both disastrous and dangerous offshoots of greek civilization, the hell let loose from the proverbial pandora's box, if you will.

they are not from disparate origins. they do not reflect fundamentally different worldviews. they do not have different intellectual genealogies. they are rooted in the same origins, have the same fundamental worldview and are of one and the same intellectual genealogy.

if you accept that western civilization is rooted in greek philosophy, and is therefore the sum of it's descendants, it follows that islam is not outside of western culture but an integral component of it.

if you are a conservative, that should lead you to embrace the religions as basically the same thing. but, if you are an iconoclast it should lead you to see their destruction as equally necessary.