The Crusades were one of the worst horrors in the history of Christian (so-called) civilization. The Crusaders, being Catholic, murdered Jews and Orthodox Christians as well as Muslims:
On the Friday (15 July) very early in the morning, we launched a general assault on the city without being able to harm it, and we were stupefied and struck with great fear. Then when the hour approached at which Our Lord Jesus Christ consented to suffer for us the torment of the cross, our knights posted on the siege engine fought fiercely among others Duke Godfrey and Count Eustace his brother. At that moment one of our knights, called Lietaud, scaled the wall of the city. As soon as he reached the top all the defenders of the city fled from the walls across the city. Our men pursued them and smitting them with their swords, as far as the temple of Solomon where there was such carnage that our men walked in blood up to their ankles...
Having broken through the pagans, our soldiers seized a large number of men and women in the temple, and they killed them or spared them depending on what seemed good to them. A large group of pagans of both sexes to whom Tancred and Gaston of Bearn had given their banners as safe conduct had taken refuge on top of the temple of Solomon. The crusaders soon ran through the city, seizing gold, silver, horses, and mules, and pillaging the houses, which were bulging with riches. Then, happy and weeping for joy, our men went to adore the sepulchre of our Savior Jesus and paid their debt to him (their vow to go on crusade). The next morning, our men climbed on to the roof of the temple, attacked the Saracens, men and women and, having drawn sword, beheaded them. Some threw themselves down from the temple. When he saw this, Tancred was filled with indignation
Anonymous History of the First Crusade, written by a knight who took part in the crusade.
http://frterry.org/History/Chapter_9...andout_117.htm