Other outbursts of fanaticism led to the destruction of churches and synagogues, [178] and the terror of such persecution led to the defection of many from the Christian Church. [179] But such oppression was contrary to the tolerant spirit of Islam, and to the teaching traditionally ascribed to the Prophet; [180] and the fanatical party tried in vain to enforce the persistent execution of these oppressive measures for the humiliation of the non-Muslim population. “The ʻulamaʼ (i.e. the learned, the clergy) consider this state of things; they weep and groan in silence, while the princes who had the power of putting down these criminal abuses only shut their eyes to them.” [181] The rules that a fanatical priesthood may lay down for the repression of unbelievers cannot always be taken as a criterion of the practice of civil governments: it is failure to realise this fact that has rendered possible the highly-coloured pictures of the sufferings of the Christians under Muhammadan rule, drawn by writers who have assumed that the prescriptions of certain Muslim theologians represented an invariable practice. Such outbursts of persecution seem in some cases to have been excited by the alleged abuse of their position by those Christians who held high posts in the service of the government; they aroused considerable hostility of feeling towards themselves by their oppression of the Muslims, it being said that they took advantage of their high position to plunder and annoy the faithful, treating them with great harshness and rudeness and despoiling them of their lands and money. Such complaints were laid before the caliphs al-Manṣūr (754–775), al-Mahdī (775–785), al-Maʼmūn (813–833), al-Mutawakkil (847–861), al-Muqtadir (908–932), and many of their successors. [182] They also incurred the odium of many Muhammadans by acting as the spies of the ʻAbbāsid dynasty and hunting down the adherents of the displaced Umayyad family. [183] At a later period, during the time of the Crusades they were accused of treasonable correspondence with the Crusaders [184] and brought on themselves severe restrictive measures which cannot justly be described as religious persecution.