The Crusades were an attempt to directly invade the Muslim heartland. At the time the justification was to free the Christian sacred places in Jerusalem from the Muslims, and for over two centuries the Crusades evoked a religious furor that still lingers over the Western mind and shapes Western culture in some ways. This continues even though contemporary mainstream Christianity has condemned the Crusades and branded them as having been no more than colonialist-driven wars that donned the cloak of Christianity while committing such atrocities as to be an affront on Christianity itself. Does the religious fervor of the Crusades "linger" over the Western mind or shape our culture? I don't think so. In contrast, too many in the Muslim world seem obsessed by the Crusades.
There is a difference between learning from the past and living in it.