Pol Pot and the Khymer Rouge were communist atheists and perped a genocide. Yet the problem is of people and political convenience more than religion or lack of it. The Hutu leaders of the Rwandan genocide claimed the Tutsi weren’t Christians to devalue them. Atheism can lead to nihilism yet politics usually isn’t about philosophical or theological issues for-itself when genocide is present; instead there are always other secular issues like race, wealth, power, resources, perversion and so forth that motivate the purge of a class of individuals. Religion or lack of it is used as an excuse for a mass purge rather than a primary cause.
I suppose there have been religious leaders that have used war to expedite proselytization- such as Mohammed who was a warrior-religion creator. The Spanish inquisition was a political purge more than something motivated by Biblical hermeneutics in error. After the Reconquista leaders wanted to purge Spain of werewolves and that took a religious form since religious affiliation was comparable to a modern political party allegiance then. That sort of political cleansing often follows wars-including post-war Germany, Iraq etc. https://uu.diva-portal.org/smash/record.jsf…
