He’s not saying that Christians are violent people, but that those who acted without conscience, allegedly in the name of Christianity, have brought shame to Christianity.
I agree, however I am unsure exactly who this describes.
Take the crusades. Most crusaders made their vow for the sake of winning back Christian land, and Christian people, to Christian rule.
When they arrived in the Holy Land, they found the fighting brutal, difficult, horrific. The hate they may have felt was enkindled by the fear and pain they experienced. Crusaders, like soldiers in every war, came in various kinds from the compassionate to the ruthless.
Historically, it is with great difficulty that we can undertake to judge Catholics of an earlier time. When a more or less unified Christendom existed, it must have seemed to the Catholics then living that Christendom existed because God willed it. Hence, to defend it doubtless seemed the right thing to do. After all, when Christendom was attacked, it was attacked as such. They did not know that eventually Christendom would be lost. How could they have known?
If the popes of an earlier time said that the time to fight was at hand, and a later pope says that there is never a time to fight, what are the faithful to think? Clearly, different popes have a different viewpoint. How can we judge which is correct, which incorrect?
For all we know, a different pope in the future will preach something different.
Would the Isrealites apologize to the Canaanites, were there any left? This brings us to what seems a conundrum: where the best way to prove God sanctions a war is to ensure that not a man, woman or child of the enemy is left. Like at Jericho.