I think we should look at the Crusades in the thinking of the times that they occurred. The idea behind them was to free the Holy Land from the grip of what was regarded as "the infidel." The fact that later participants behaved no better than gangsters should not for example denigrate shall we say The Childrens' Crusade. Conquest and the acquisition of land was the role for many so called civilised people, no matter what side of the religious divide they came from and later crusaders were not always in the game for the good of their souls.