After 30+ years of observing and taking part in debates about history with many of my fellow atheists I can safely claim that most atheists are historically illiterate. This is not particular to atheists: they tend to be about as historically illiterate as most people, since historical illiteracy is pretty much the norm. But it does not mean that when most (not all) atheists comment about history or, worse, try to use history in debates about religion, they are usually doing so with a grasp of the subject that is stunted at about high school level.
. . . All too often many atheists can be polemicists when dealing with the past, only crediting information or analysis that fits an argument against religion they are trying to make while downplaying, dismissing or ignoring evidence or analysis that does not fit their agenda.