How is it that fascism can be seen as a product of Western civilization?
In one way, it is obvious that fascism was a product of one western nation at one time. The more important question is whether all western nations inevitably descend into fascism, and again, it is equally obvious that such has not been the case. Thus it is important to refine your question to consider what factors make some but not other nations descend into fascism.
In the case of Germany, one can look at two areas. The first is the culture of Arayanism. This movement began as an attempt at nation-building (the unification of the German states into a single nation was a late -- 19th century -- phenomenon); thus an active ideology of nationalism was a factor. Second, Germany had been very harshly treated at the end of WW I, and was enduring substantial economic hardship, making many Germans more prone to listening to demagogues like Hitler than they might have been otherwise. Thus one can say that fascism can be, but is not necessarily, a product of 2 aspects of certain western cultures.