"it wasn't the Romans it was the Jews" is also a fact of the most mainstream versions of Christian/Catholic beliefs. It's also a fact of their beliefs that Jesus himself was Jewish, and I was taught both of those things when growing up in a religious school system without ever being taught to blame or hate Jewish people for it because Jewish people were also regularly victims of oppression in the bible being saved whether by Moses or God himself or others. Someone using it as an example of religious infighting doesn't automatically mean it's being used as an antisemitic argument. Whether you take issue with how that account of events came to exist historically isn't the fault of the other commenter, it is still part of the mythos as most people know it, and the conversation was referring specifically to the mythos. Jesus forgiving his own people and telling god "they know not what they do" is kind of an important aspect of his sacrifice and martyrdom.