The same biblical evidence was used to argue opposite positions on crusade

Evidence

The Christian canon of Muslim behaviour, that is, the received Christian opinion as to what Muslims actually did, was partly formed by the tendency of misconceptions to snowball, and to confirm as well as to add to one another. Mere repetition is enough to bring unshakable conviction; and once it had been asserted that Islamic teaching was sexually lax, every example of laxity would be noticed from that moment, and, once notified, attributed to the doctrine. … If we suppose that there were an equal number of similar offences committed by Christians and by Muslims in any given time, in the former case they would be seen as having occurred in spite of doctrine, so that each individual case would be an exception, and in the latter it would be assumed that doctrine was the cause of whatever happened. Moreover, if it were not a matter of seeking examples to prove a thesis, each particular episode would be less likely to be noticed in the first place. … More often the polemic purpose guided the selection of facts, and there were few cases indeed where mistakes were made that showed Islam in a less disadvantageous light than was necessary. — Norman Daniel, Islam and the West, 1362 (#exemplifies, via linked claim)

For any outsider, and surely for most Muslims, this would be regarded as defaming the Prophet in the worst possible way; in Iran this was done for the exact opposite purpose. Claiming that the Prophet instigated murder had as its purpose not to defame the Prophet but to justify murder by showing that the Prophet himself had encouraged it. It is an argument with far-reaching impli­ cations and devastating consequences. — Bernard Lewis, From Babel to Dragomans, 586 (#complicates, via linked claim)

The doctrines of Crusade and jihad here approximate, first, in the willingness to tolerate people of an alien religion only as subjects (though their status within Christendom in theory and practice was less safe than in Islam); in the direction of holy war against all kinds of rebels and dissenters; and in the insistence on duly constituted authority for waging war. — Norman Daniel, Islam and the West, 1823 (#complicates, via linked claim)

Categorization

• XREF: connects to: Identical source material can yield opposite religious impressions; Competing Christian confessions read the same conquests from opposing viewpoints; Arguments against the Qur’an’s origin apply equally to Christian scripture. — Norman Daniel, Islam and the West, 1442 (+12 more)

Broader Connections

• Anti-Islam polemics made identical Christian behavior an exception and Muslim behavior a doctrinal proof #exemplifies (1.00) — Norman Daniel, Islam and the West, 1362
• The same claim about the Prophet can serve opposite moral purposes #complicates (0.90) — Bernard Lewis, From Babel to Dragomans, 586
• Crusade and jihad shared core doctrinal assumptions about religious tolerance and authority #complicates (0.90) — Norman Daniel, Islam and the West, 1823
• Theology can dispute only with those sharing a common scripture #complicates (0.80) — Gil Anidjar, The Jew, the Arab, 236
• Medieval Christian-Muslim disputation mostly argued from premises neither side shared #complicates (0.75)
• Christian-Muslim controversy necessarily centers on their fixed points of doctrinal disagreement #complicates (0.70)