"Extremist Sunni preachers based in Saudi Arabia or Kuwait abuse Shia as “idol-worshippers” – the intolerant language of Wahhabi exclusivity. Iranians are scorned as “Safawis”, a pejorative reference to the 16th-century Safavid dynasty. Fanatical jihadis such as the Islamic State justify the killing of “apostates” under the doctrine of “takfir”.