The very fact that thinkers of the Renaissance thought that is itself a form of whitewashing. The very books that sparked the Renaissance were kept alive by the Islamic empires. The Renaissance thinkers, in order to advance their Christianity, wanted to ignore the Islamic contributions to their culture. In certain cases, like the Mozarabs and the Moors, Islamic architecture and customs deeply influenced what later became Catholic states. While the OP may be overly forceful, the repudiation of Islamic empires from the Middle Ages onward is a massive disservice to history. Let's not forget that the Ottomans were on the German side of WWI, the same state that traced its lineage through the Byzantines back to the ancient Islamic caliphates themselves.