One of the ways I have seen Muslim leaders promote Islam is by talking about the glory of the Islamic civilization. The Islamic empire is said to be a system of justice and responsible for everything good in the world. Very often when these claims are made the Western Christian civilization is criticised as corrupt and brutal. This approach to promoting Islam is successful for a few reasons:
Most Westerners feel some shame over the history of their empires, and so when a speaker attacks Western culture they acknowledge these faults.
Most Westerners have little knowledge of Islamic history, and so assume that what the Islamic leader says about the Islamic empire must be true.
Hence in the study of Islam in the West, the dominant convention is that a critical approach is reserved for the Christian past but forbidden for the Muslim past. ... The net result is a romantic picture of the history of Islam avoiding and sometimes denying such issues as the jihadists’ slaughter and massive enslavement of traditional African believers. (John Alembillah Azumah, The Legacy of Arab-Islam in Africa, pp. xiv-xv.)
In this article I invite you to begin to learn about Islam's involvement in slavery. Islam has had a major role in the history of slavery beginning with Muhammad, and taking slaves from Europe across to Indonesia and down into Africa. But unlike the Western empires, Islam has never apologised and feels no shame. In fact Muslim leaders boast of their empire as the "Golden Period" and hide its corruption and brutality.