Religious violence has a long and terrible history.
From Sapiens by Yuval Noah Harari:
“In the 300 years from the crucifixion of Christ to the conversion of Emperor Constantine, polytheistic Roman emperors initiated no more than four general persecutions of Christians. Local administrators and governors incited some anti-Christian violence of their own. Still, if we combine all the victims of all these persecutions, it turns out that in these three centuries, the polytheistic Romans killed no more than a few thousand Christians. In contrast, over the course of the next 1,500 years, Christians slaughtered Christians by the millions to defend slightly different interpretations of the religion of love and compassion.”
And he adds this for perspective:
“On 23 August 1572, French Catholics who stressed the importance of good deeds attacked communities of French Protestants who highlighted God’s love for humankind. In this attack, the St Bartholomew’s Day Massacre, between 5,000 and 10,000 Protestants were slaughtered in less than twenty-four hours. … More Christians were killed by fellow Christians in those twenty-four hours than by the polytheistic Roman Empire throughout its entire existence.”
Harari’s book is an epic survey of the history of humans on earth. It’s filled with sobering details like this along with a hopeful perspective on how far we have come.