Today (22 July 2019) is both the feast day of Mary Magdalene and the 810th anniversary of the Beziers Massacre, in which the early Crusaders murdered everyone in the town, included those who had taken refuge in the Mary Magdalene church.
It was this relatively indiscriminate slaughter by the Crusaders which inspired the well-known saying,
"Kill them all, and let God sort them out."
The Crusaders were supposed to be murdering only heretics (especially Cathars) and Jews, but in the heat of the raid it was recognized that some people would lie about whether or not they were good Catholics so it was felt to be more prudent just to kill everyone, including those taking refuge in churches.
Various accounts in the aftermath put the death toll at anywhere from 7,000 to 20,000 souls.
Today you can tour the castles and churches of Cathar congregations all over southern France, especially around Toulouse.