Back when ISIS was still expanding into the multi-ethnic and religiously diverse northern Iraq, not just Yazidis but also the country’s 1 million Christians were some of their main targets. They were asked to either convert or leave, otherwise they would be killed. All along, churches were being bombed or burnt to the ground.
Most of the Christians that used to inhabit those areas of the Levant where ISIS now rules have been displaced, in an act of religious/ethnic cleansing more thorough than any that Saddam had ever achieved. And ISIS is still working through the backlog of churches to be destroyed. Only recently they destroyed one that was described as equivalent to Canterbury Cathedral.
Muslim scholars I have spoken to have stated that such actions are completely un-Islamic, strictly against Sharia and a blasphemy against the Prophet Muhammad more serious than any they can think of from history. The Qur’an commands Muslims to follow Muhammad and his example:
And the Prophet Mohammad was very clear about how Muslims should treat Christians. He entered a treaty with them which deserves to be quoted in full here: