Historical revisionism on an incredible scale.
I don't think the Carlogians and Muslims ever actually interacted at all, and it's not like "the Muslims" and "the west" were unified entities struggling against each other. They were different empires struggling against different empires, some of which happened to be Christian and others which happened to be Muslim. The Crusades was, perhaps, a response to a war between the Byzantines and a Muslim empire, but the Catholics never actually helped the Byzantines, and decided to take the Holy Land, which was never part of the mission. And the only long term effect of the crusades was when the Catholics destroyed the Byzantine empire (a rump state was refounded, eventually retook Constantinople, but it was hugely weakened from the Catholic destruction and never rose to the power of the state which the Catholics destroyed). Why did Christians destroy other Christians?